Mention data persistence in WebGL in README

Author: gilzoide

README.md

@@ -13,6 +13,7 @@ This package provides the excelent [SQLite-net](https://github.com/praeclarum/sq
   + Enabled modules: [R\*Tree](https://sqlite.org/rtree.html), [Geopoly](https://sqlite.org/geopoly.html), [FTS5](https://sqlite.org/fts5.html), [Built-In Math Functions](https://www.sqlite.org/lang_mathfunc.html)
   + Prebuilt for Windows, Linux, macOS, Android and WebGL
   + Built from source in iOS, tvOS and visionOS projects
+  + Supports persisting data in WebGL builds by using a [custom VFS backed by Indexed DB](https://github.com/gilzoide/idbvfs).
 
 
 ## Optional packages