Add missing sponsors section

Author: kzu

readme.md

@@ -55,4 +55,6 @@ attribute), removes all its child nodes and moves (if necessary) the
 `PrivateAssets` child element to an attribute.
 
 This is done automatically whenever the analyzer runs, and nothing 
-is saved unless a node was cleaned.
+is saved unless a node was cleaned.
+
+<!-- include https://github.com/devlooped/sponsors/raw/main/footer.md -->