Fix onLanguage activation event (#13630)

According to the the VSCode documentation `onLanguage` (without any
language specified) is a valid activation event.
This is used in the built-in emmet extension for example.
Beforehand extensions with this event were not triggered.
With this commit the extensions with `onLanguage` are activated,
when the first language is loaded.

packages/plugin-ext/src/hosted/browser/hosted-plugin.ts

@@ -409,6 +409,7 @@ export class HostedPluginSupport extends AbstractHostedPluginSupport<PluginManag
     }
 
     async activateByLanguage(languageId: string): Promise<void> {
+        await this.activateByEvent('onLanguage');
         await this.activateByEvent(`onLanguage:${languageId}`);
     }