Update documentation with sprite sources

docs/json/category.md

@@ -10,3 +10,33 @@ Dynamic Asset Generator can be used to add or overwrite assets or data using JSO
 ```
 
 Where the `type` defines what sort of generator it is and what it does; the other specified arguments will depend on the type of generator.
+
+## Sprite Sources
+
+Dynamic Asset Generator's texture sources can also be used as a sprite source in a texture atlas, similar to vanilla's paletted
+permutations. To use them this way, a sprite source of type `dynamic_asset_generator:tex_sources` should be added to the texture
+atlas JSON file you wish to generate textures for. This sprite source takes several parameters:
+* `sources` - a map of the resource locations of textures to generate, to the texture source to use to generate them.
+* `location` - optional; a path representing a folder to search for texture sources to generate.
+
+For instance, if the following were placed at `assets/minecraft/atlases/blocks.json`:
+```json
+{
+  "sources": [
+    {
+      "type": "dynamic_asset_generator:tex_sources",
+      "sources": {
+        "minecraft:block/clay": {
+          "type" : "dynamic_asset_generator:texture",
+          "path" : "minecraft:block/iron_block"
+        }
+      },
+      "location": "namespace:path"
+    }
+  ]
+}
+```
+Then the texture for clay would be replaced with the texture for iron, and a file placed at `assets/minecraft/namespace/path/block/end_stone.json`
+containing a texture source would replace the texture for end stone. This sprite source takes the same types of texture sources
+as [Texture Generation](texsources/category.md). If the texture source accesses other textures, the sprite source will attempt
+to generate animation metadata from those textures.