Resolve #6804

Implement unison reload

src/client/scripts/unison-reload.ts

@@ -0,0 +1,12 @@
+// SafariがBroadcastChannel未実装なのでライブラリを使う
+import { BroadcastChannel } from 'broadcast-channel';
+
+const ch = new BroadcastChannel<boolean | undefined>('reload');
+
+// BroadcastChannelを用いて、クライアントが一斉にreloadするようにします。
+export function unisonReload(forcedReload?: boolean) {
+    ch.postMessage(forcedReload);
+    location.reload(forcedReload as boolean);
+}
+
+ch.addEventListener('message', forcedReload => location.reload(forcedReload as boolean));