Allow all lossless image formats to be used for VRS texture project setting

WebP can also be lossy, but the class reference now warns about the
requirement to use a lossless format for the VRS texture to work correctly.

doc/classes/ProjectSettings.xml

@@ -2265,7 +2265,20 @@
 			Set the default Variable Rate Shading (VRS) mode for the main viewport. See [member Viewport.vrs_mode] to change this at runtime, and [enum Viewport.VRSMode] for possible values.
 		</member>
 		<member name="rendering/vrs/texture" type="String" setter="" getter="" default="&quot;&quot;">
-			If [member rendering/vrs/mode] is set to texture, this is the path to default texture loaded as the VRS image.
+			If [member rendering/vrs/mode] is set to [b]Texture[/b], this is the path to default texture loaded as the VRS image.
+			The texture [i]must[/i] use a lossless compression format so that colors can be matched precisely. The following VRS densities are mapped to various colors, with brighter colors representing a lower level of shading precision:
+			[codeblock]
+			- 1x1 = rgb(0, 0, 0)     - #000000
+			- 1x2 = rgb(0, 85, 0)    - #005500
+			- 2x1 = rgb(85, 0, 0)    - #550000
+			- 2x2 = rgb(85, 85, 0)   - #555500
+			- 2x4 = rgb(85, 170, 0)  - #55aa00
+			- 4x2 = rgb(170, 85, 0)  - #aa5500
+			- 4x4 = rgb(170, 170, 0) - #aaaa00
+			- 4x8 = rgb(170, 255, 0) - #aaff00 - Not supported on most hardware
+			- 8x4 = rgb(255, 170, 0) - #ffaa00 - Not supported on most hardware
+			- 8x8 = rgb(255, 255, 0) - #ffff00 - Not supported on most hardware
+			[/codeblock]
 		</member>
 		<member name="threading/worker_pool/low_priority_thread_ratio" type="float" setter="" getter="" default="0.3">
 		</member>

doc/classes/Viewport.xml

@@ -343,6 +343,19 @@
 		</member>
 		<member name="vrs_texture" type="Texture2D" setter="set_vrs_texture" getter="get_vrs_texture">
 			Texture to use when [member vrs_mode] is set to [constant Viewport.VRS_TEXTURE].
+			The texture [i]must[/i] use a lossless compression format so that colors can be matched precisely. The following VRS densities are mapped to various colors, with brighter colors representing a lower level of shading precision:
+			[codeblock]
+			- 1x1 = rgb(0, 0, 0)     - #000000
+			- 1x2 = rgb(0, 85, 0)    - #005500
+			- 2x1 = rgb(85, 0, 0)    - #550000
+			- 2x2 = rgb(85, 85, 0)   - #555500
+			- 2x4 = rgb(85, 170, 0)  - #55aa00
+			- 4x2 = rgb(170, 85, 0)  - #aa5500
+			- 4x4 = rgb(170, 170, 0) - #aaaa00
+			- 4x8 = rgb(170, 255, 0) - #aaff00 - Not supported on most hardware
+			- 8x4 = rgb(255, 170, 0) - #ffaa00 - Not supported on most hardware
+			- 8x8 = rgb(255, 255, 0) - #ffff00 - Not supported on most hardware
+			[/codeblock]
 		</member>
 		<member name="world_2d" type="World2D" setter="set_world_2d" getter="get_world_2d">
 			The custom [World2D] which can be used as 2D environment source.

scene/main/scene_tree.cpp

@@ -1450,7 +1450,7 @@ SceneTree::SceneTree() {
 	ProjectSettings::get_singleton()->set_custom_property_info("rendering/vrs/texture",
 			PropertyInfo(Variant::STRING,
 					"rendering/vrs/texture",
-					PROPERTY_HINT_FILE, "*.png"));
+					PROPERTY_HINT_FILE, "*.bmp,*.png,*.tga,*.webp"));
 	if (vrs_mode == 1 && !vrs_texture_path.is_empty()) {
 		Ref<Image> vrs_image;
 		vrs_image.instantiate();