Fix license info and lint

src/Terminal.ts

@@ -2284,11 +2284,13 @@ export class Terminal extends EventEmitter implements ITerminal, IInputHandlingT
   }
 
   private visualBell(): boolean {
-    return this.options.bellStyle == 'visual' || this.options.bellStyle == 'both';
+    return this.options.bellStyle === 'visual' ||
+        this.options.bellStyle === 'both';
   }
 
   private soundBell(): boolean {
-    return this.options.bellStyle == 'sound' || this.options.bellStyle == 'both';
+    return this.options.bellStyle === 'sound' ||
+        this.options.bellStyle === 'both';
   }
 
   private preloadBellSound(): void {

src/utils/Sounds.ts

@@ -1 +1,9 @@
+/**
+ * @license MIT
+ */
+
+// Source: https://freesound.org/people/altemark/sounds/45759/
+// This sound is released under the Creative Commons Attribution 3.0 Unported
+// (CC BY 3.0) license. It was created by 'altemark'. No modifications have been
+// made, apart from the conversion to base64.
 export const BellSound = 'data:audio/wav;base64,UklGRigBAABXQVZFZm10IBAAAAABAAEARKwAAIhYAQACABAAZGF0YQQBAADpAFgCwAMlBZoG/wdmCcoKRAypDQ8PbRDBEQQTOxRtFYcWlBePGIUZXhoiG88bcBz7HHIdzh0WHlMeZx51HmkeUx4WHs8dah0AHXwc3hs9G4saxRnyGBIYGBcQFv8U4RPAEoYRQBACD70NWwwHC6gJOwjWBloF7gOBAhABkf8b/qv8R/ve+Xf4Ife79W/0JfPZ8Z/wde9N7ijtE+wU6xvqM+lb6H7nw+YX5mrlxuQz5Mzje+Ma49fioeKD4nXiYeJy4pHitOL04j/jn+MN5IPkFOWs5U3mDefM55/ogOl36m7rdOyE7abuyu8D8Unyj/Pg9D/2qfcb+Yn6/vuK/Qj/lAAlAg==';