TodoListWebview subscriptions

TodoListWebview.ts

public open(pageId: string, opts: { onClose: () => void }) {
  // ...
  
  this.context.subscriptions.push(
    webviewPanel.webview.onDidReceiveMessage(
      (msg) => envelopeServer.receive(msg, this.api),
      webviewPanel.webview,
      this.context.subscriptions
    )
  );

  webviewPanel.onDidDispose(
    () => {
      envelopeServer.stopInitPolling();
      opts.onClose();
    },
    webviewPanel.webview,
    this.context.subscriptions
  );

  envelopeServer.startInitPolling();
}