🎉 Add TypeScript typings

Author: LinusU

index.d.ts

@@ -0,0 +1,10 @@
+declare interface Loudness {
+  getMuted(): Promise<boolean>
+  getVolume(): Promise<number>
+  setMuted(muted: boolean): Promise<void>
+  setVolume(volume: number): Promise<void>
+}
+
+declare const loudness: Loudness
+
+export = loudness