Provide a status widget "Language Service"

[angelozerr]

The Jetbrains support provides a status widget to show which language servers are associated with the current file:

It would be nice to have this feature.

When I see https://www.jetbrains.com/help/idea/typescript-support.html#ws_ts_use_ts_service_checkbox I think we should use

https://github.com/JetBrains/intellij-community/blob/master/platform/lang-api/src/com/intellij/platform/lang/lsWidget/LanguageServiceWidgetItemsProvider.kt but it seems this class exists since february, so we cannot use it for the moment because we need to try to cover one year.