Add SharingCloud plugin (#139)

* Update README.md

* Update README.md

---------

Co-authored-by: Stephen Celis <[email protected]>

Author: KeithBird

README.md

@@ -252,7 +252,9 @@ Sharing is built with extensibility in mind, and there are a number of community
 available to enhance your applications:
 
   * [SharingGRDB](https://github.com/pointfreeco/sharing-grdb): A lightweight replacement for
-    SwiftData and the `@Query` macro.
+    SwiftData and the `@Query` macro.    
+  * [SharingCloud](https://github.com/KeithBird/sharing-cloud): Sync shared data across devices via
+    iCloud.
 
 If you'd like to contribute a library, please [open a PR][library-pr] with a link to it!