Create AudioContext only when needed

ts/util/Sound.ts

@@ -11,7 +11,7 @@ export type SoundOpts = {
 export class Sound {
   static sounds = new Map();
 
-  private readonly context = new AudioContext();
+  private static context: AudioContext | undefined;
 
   private readonly loop: boolean;
 
@@ -59,6 +59,13 @@ export class Sound {
     }
   }
 
+  private get context(): AudioContext {
+    if (!Sound.context) {
+      Sound.context = new AudioContext();
+    }
+    return Sound.context;
+  }
+
   static async loadSoundFile(src: string): Promise<ArrayBuffer> {
     const xhr = new XMLHttpRequest();