Texture replacement: Add [indexed] to the generated textures.ini

Document the section and the supported files in the template.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

GPU/Common/TextureReplacer.cpp

@@ -1160,6 +1160,18 @@ ignoreAddress = false    # Reduces duplicates at the cost of making hash less re
 # You can enforce specific filtering modes with this. Available modes are linear, nearest, auto. See the docs.
 # Example: 08d3961000000909ba70b2af = nearest
 
+[indexed]
+# Marks replacement images that hold palette indices instead of colors, for games that use many palettes
+# for one texture or let the player change them. The game's current palette colors the image, so a single
+# high resolution image works with every palette.
+# Supported files: PNG only, either a palette (indexed) PNG, where the palette index of each pixel is used
+# (the colors in the file's palette are ignored), or a grayscale PNG of at most 8 bits, where the gray value
+# is the index. RGB/RGBA PNG, DDS, KTX2 and ZIM files can't be used here, and there are no mipmaps.
+# The image can have any resolution, for example 4x the original. The index values must match what the game uses.
+# Use the hashes section to name the file, with the CLUT hash set to 00000000 to match every palette.
+# Format: <address><clut hash><texture hash> = true
+# Example: 08d3961000000000ba70b2af = true
+
 [reducehashranges]
 # Lets you set texture sizes where the hash range is reduced by a factor. See the docs.
 # Example: