message: Implement the application Quit command
diff: @@ -344,6 +344,7 @@ class Main {
  const commands = extensionManager.getExtensionContextByName("internal-commands").getExtensionContext().commands;
  commands.registerCommand("extraterm:application.openCommandPalette", () => this.commandOpenCommandPalette());
  commands.registerCommand("extraterm:application.newWindow", () => this.commandNewWindow());
  + commands.registerCommand("extraterm:application.quit", () => this.commandQuit());
  commands.registerCommand("extraterm:window.newTerminal", (args: any) => this.commandNewTerminal(args));
  commands.registerCommand("extraterm:window.openSettings", (args: any) => this.commandOpenSettings(args));
  commands.registerCommand("extraterm:window.focusTabLeft", () => this.commandFocusTabLeft());
  @@ -431,6 +432,12 @@ class Main {
  this.openWindow();
  }
  + commandQuit(): void {
  + while (this.#windows.length !== 0) {
  + this.#disposeWindow(this.#windows[0]);
  + }
  + }
  +
  async commandNewTerminal(args: {sessionUuid?: string, sessionName?: string, workingDirectory?: string}): Promise<void> {
  let sessionConfiguration: SessionConfiguration = this.#configDatabase.getSessionConfig()[0];
  if (args.sessionUuid != null) {
  