Add note for hosting asset icons on GitHub (#9125)

* Add note for hosting asset icons on GitHub

---------

Co-authored-by: Max Hilbrunner <[email protected]>
(cherry picked from commit 1c09d6a704074cd9d40ce2059a603d6ddbf3600f)

community/asset_library/submitting_to_assetlib.rst

@@ -178,6 +178,10 @@ is required in the submission form here as well.
     The **icon** must be square (1:1 aspect ratio). It should have a minimum
     resolution of 128×128 pixels.
 
+.. note::
+
+    For icons hosted on GitHub, URLs must be provided in the form of `https://raw.githubusercontent.com/<user>/<project>/<branch>/Icon.png`.
+
 * **License**:
     The license under which you are distributing the asset. The list
     includes a variety of free and open source software licenses, such as GPL