Document image size limits

This closes #30238.

(cherry picked from commit 5497cec7a1c6e724f979b506a53bb07b5f71ce17)

doc/classes/Image.xml

@@ -5,6 +5,7 @@
 	</brief_description>
 	<description>
 		Native image datatype. Contains image data, which can be converted to a [Texture], and several functions to interact with it. The maximum width and height for an [Image] are [constant MAX_WIDTH] and [constant MAX_HEIGHT].
+		[b]Note:[/b] The maximum image size is 16384×16384 pixels due to graphics hardware limitations. Larger images will fail to import.
 	</description>
 	<tutorials>
 	</tutorials>

doc/classes/ImageTexture.xml

@@ -5,6 +5,7 @@
 	</brief_description>
 	<description>
 		A [Texture] based on an [Image]. Can be created from an [Image] with [method create_from_image].
+		[b]Note:[/b] The maximum image size is 16384×16384 pixels due to graphics hardware limitations. Larger images will fail to import.
 	</description>
 	<tutorials>
 	</tutorials>