Add descriptions to a few RenderingDevice's PipelineDynamicStateFlags

doc/classes/RenderingDevice.xml

@@ -2142,8 +2142,10 @@
 			Represents the size of the [enum BlendOperation] enum.
 		</constant>
 		<constant name="DYNAMIC_STATE_LINE_WIDTH" value="1" enum="PipelineDynamicStateFlags" is_bitfield="true">
+			Allows dynamically changing the width of rendering lines.
 		</constant>
 		<constant name="DYNAMIC_STATE_DEPTH_BIAS" value="2" enum="PipelineDynamicStateFlags" is_bitfield="true">
+			Allows dynamically changing the depth bias.
 		</constant>
 		<constant name="DYNAMIC_STATE_BLEND_CONSTANTS" value="4" enum="PipelineDynamicStateFlags" is_bitfield="true">
 		</constant>