Update `ProjectSettings` HDR 2D documentation to include Compatibility support.

doc/classes/ProjectSettings.xml

@@ -3375,8 +3375,9 @@
 			The default compression factor for lossless WebP. Decompression speed is mostly unaffected by the compression factor. Supported values are 0 to 100.
 		</member>
 		<member name="rendering/viewport/hdr_2d" type="bool" setter="" getter="" default="false">
-			If [code]true[/code], enables [member Viewport.use_hdr_2d] on the root viewport. 2D rendering will use a high dynamic range (HDR) format framebuffer matching the bit depth of the 3D framebuffer. When using the Forward+ renderer this will be an [code]RGBA16[/code] framebuffer, while when using the Mobile renderer it will be an [code]RGB10_A2[/code] framebuffer. Additionally, 2D rendering will take place in linear color space and will be converted to sRGB space immediately before blitting to the screen. Practically speaking, this means that the end result of the Viewport will not be clamped into the [code]0-1[/code] range and can be used in 3D rendering without color space adjustments. This allows 2D rendering to take advantage of effects requiring high dynamic range (e.g. 2D glow) as well as substantially improves the appearance of effects requiring highly detailed gradients.
-			[b]Note:[/b] This setting will have no effect when using the Compatibility renderer, which always renders in low dynamic range for performance reasons.
+			If [code]true[/code], enables [member Viewport.use_hdr_2d] on the root viewport. 2D rendering will use a high dynamic range (HDR) format framebuffer matching the bit depth of the 3D framebuffer. When using the Forward+ or Compatibility renderer, this will be an [code]RGBA16[/code] framebuffer. When using the Mobile renderer, it will be an [code]RGB10_A2[/code] framebuffer.
+			Additionally, 2D rendering will take place in linear color space and will be converted to sRGB space immediately before blitting to the screen (if the Viewport is attached to the screen).
+			Practically speaking, this means that the end result of the Viewport will not be clamped to the [code]0-1[/code] range and can be used in 3D rendering without color space adjustments. This allows 2D rendering to take advantage of effects requiring high dynamic range (e.g. 2D glow) as well as substantially improves the appearance of effects requiring highly detailed gradients.
 			[b]Note:[/b] This property is only read when the project starts. To toggle HDR 2D at runtime, set [member Viewport.use_hdr_2d] on the root [Viewport].
 		</member>
 		<member name="rendering/viewport/transparent_background" type="bool" setter="" getter="" default="false">

doc/classes/RenderingServer.xml

@@ -4242,7 +4242,9 @@
 			<param index="0" name="viewport" type="RID" />
 			<param index="1" name="enabled" type="bool" />
 			<description>
-				If [code]true[/code], 2D rendering will use a high dynamic range (HDR) format framebuffer matching the bit depth of the 3D framebuffer. When using the Forward+ or Compatibility rendering method this will be an [code]RGBA16[/code] framebuffer, while when using the Mobile rendering method it will be an [code]RGB10_A2[/code] framebuffer. Additionally, 2D rendering will take place in linear color space and will be converted to sRGB space immediately before blitting to the screen (if the Viewport is attached to the screen). Practically speaking, this means that the end result of the Viewport will not be clamped into the [code]0-1[/code] range and can be used in 3D rendering without color space adjustments. This allows 2D rendering to take advantage of effects requiring high dynamic range (e.g. 2D glow) as well as substantially improves the appearance of effects requiring highly detailed gradients. This setting has the same effect as [member Viewport.use_hdr_2d].
+				If [code]true[/code], 2D rendering will use a high dynamic range (HDR) format framebuffer matching the bit depth of the 3D framebuffer. When using the Forward+ or Compatibility renderer, this will be an [code]RGBA16[/code] framebuffer. When using the Mobile renderer, it will be an [code]RGB10_A2[/code] framebuffer.
+				Additionally, 2D rendering will take place in linear color space and will be converted to sRGB space immediately before blitting to the screen (if the Viewport is attached to the screen).
+				Practically speaking, this means that the end result of the Viewport will not be clamped to the [code]0-1[/code] range and can be used in 3D rendering without color space adjustments. This allows 2D rendering to take advantage of effects requiring high dynamic range (e.g. 2D glow) as well as substantially improves the appearance of effects requiring highly detailed gradients. This setting has the same effect as [member Viewport.use_hdr_2d].
 			</description>
 		</method>
 		<method name="viewport_set_use_occlusion_culling">

doc/classes/Viewport.xml

@@ -459,7 +459,9 @@
 			See also [member ProjectSettings.rendering/anti_aliasing/quality/use_debanding] and [method RenderingServer.viewport_set_use_debanding].
 		</member>
 		<member name="use_hdr_2d" type="bool" setter="set_use_hdr_2d" getter="is_using_hdr_2d" default="false">
-			If [code]true[/code], 2D rendering will use a high dynamic range (HDR) format framebuffer matching the bit depth of the 3D framebuffer. When using the Forward+ or Compatibility rendering method this will be an [code]RGBA16[/code] framebuffer, while when using the Mobile rendering method it will be an [code]RGB10_A2[/code] framebuffer. Additionally, 2D rendering will take place in linear color space and will be converted to sRGB space immediately before blitting to the screen (if the Viewport is attached to the screen). Practically speaking, this means that the end result of the Viewport will not be clamped into the [code]0-1[/code] range and can be used in 3D rendering without color space adjustments. This allows 2D rendering to take advantage of effects requiring high dynamic range (e.g. 2D glow) as well as substantially improves the appearance of effects requiring highly detailed gradients.
+			If [code]true[/code], 2D rendering will use a high dynamic range (HDR) format framebuffer matching the bit depth of the 3D framebuffer. When using the Forward+ or Compatibility renderer, this will be an [code]RGBA16[/code] framebuffer. When using the Mobile renderer, it will be an [code]RGB10_A2[/code] framebuffer.
+			Additionally, 2D rendering will take place in linear color space and will be converted to sRGB space immediately before blitting to the screen (if the Viewport is attached to the screen).
+			Practically speaking, this means that the end result of the Viewport will not be clamped to the [code]0-1[/code] range and can be used in 3D rendering without color space adjustments. This allows 2D rendering to take advantage of effects requiring high dynamic range (e.g. 2D glow) as well as substantially improves the appearance of effects requiring highly detailed gradients.
 		</member>
 		<member name="use_occlusion_culling" type="bool" setter="set_use_occlusion_culling" getter="is_using_occlusion_culling" default="false">
 			If [code]true[/code], [OccluderInstance3D] nodes will be usable for occlusion culling in 3D for this viewport. For the root viewport, [member ProjectSettings.rendering/occlusion_culling/use_occlusion_culling] must be set to [code]true[/code] instead.