[unity] Improved readme.md documentation of Addressables extension module.

spine-unity/Modules/com.esotericsoftware.spine.addressables/Documentation/README.md

@@ -2,6 +2,22 @@
 
 This experimental plugin provides integration of Addressables on-demand texture loading for the spine-unity runtime. Please be sure to test this package first and create backups of your project before using.
 
+The Spine Addressables Extension module covers all necessary steps to automatically replace your textures with low-resolution placeholder textures and loading the high-resolution textures upon request. The textures are automatically replaced with the low-resolution texture when building your game executable via a pre-build step (and reset to the high-resolution textures afterwards in the post-build step). There is no additional coding required.
+
 ### Usage
 
-First declare your target Material textures as addressable. Then select the SpineAtlasAsset, right-click the SpineAtlasAsset Inspector heading and select 'Add Addressables Loader'. This generates an 'AddressableTextureLoader' asset providing configuration parameters and sets up low-resolution placeholder textures which are automatically assigned in a pre-build step when building your game executable.
+The following steps are all that is required to setup your textures to be replaced with low resolution placeholders and downloaded on-demand:
+
+1. Declare your original high-resolution target Material textures as [addressable](https://learn.unity.com/course/get-started-with-addressables).
+2. Select the `SpineAtlasAsset`, right-click the `SpineAtlasAsset` Inspector heading and select `Add Addressables Loader`. This generates an `AddressableTextureLoader` asset. This asset provides configuration parameters and sets up low-resolution placeholder textures which are automatically assigned in a pre-build step when building your game executable.
+3. Build your Addressables content as usual.
+
+From now on when building your game executable, the low resolution placeholder textures are automatically assigned initially and the corresponding high-resolution textures loaded on-demand.
+
+### Editor Preview
+
+Please note that the low-resolution textures are activated only when building the game executable, they are usually never shown in the Editor, also not in play-mode.
+
+If you still want to temporarily assign the low-resolution placeholder textures for preview purposes, select the desired `AddressableTextureLoader` asset and hit `Testing` - `Assign Placeholders` to temporarily replace the high-resolution textures with their low-resolution placeholders. You can then see the high-resolution textures loaded on-demand when entering play-mode. Note that this is for preview purposes only and has no effect on the built game executable.
+
+Placeholder textures need not be assigned manually, as these are automatically assigned via a pre-build step (and reset afterwards in the post-build step).