Readme: added rust to list of supported LS

Also added statement on Kotlin and Dart coming soon

README.md

@@ -55,12 +55,15 @@ With Serena, we provide
      * Ruby (untested)
      * Go (untested)
      * C# (untested)
+     * Rust (untested)
    These languages are supported by the language server library [multilspy](https://github.com/microsoft/multilspy), which Serena uses under the hood.
    But we did not explicitly test whether the support for these languages actually works.
        
 Further languages can, in principle, easily be supported by providing a shallow adapter for a new language server
 implementation.
 
+Coming soon: Kotlin and Dart.
+
 ## Table of Contents
 
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