Add instructions to use official release builds

The previous installation instructions made no mention of the release builds,
telling new users to build the server from scratch when there already
were finished builds to use :)

Author: fatso83

README.md

@@ -77,7 +77,12 @@ extension at
 
 ## Install
 
-You can build language server from sources. See [build.md](doc/devel/build.md) for details.
+The official [releases][releases] contains ready-built packages for
+various platforms and architectures and should be your first choice when trying out the language server.
+
+You can also build the language server from source. See [build.md](doc/devel/build.md) for details.
+
+[releases]: https://github.com/AdaCore/ada_language_server/releases
 
 ## Usage