message: Export COLORTERM=truecolor to show that we support 24bit color
diff: @@ -572,7 +572,8 @@ this._log.debug("tab RMB");
  private _createPtyForTerminal(newTerminal: EtTerminal, sessionUuid: string): void {
  const extraEnv = {
  - [EXTRATERM_COOKIE_ENV]: newTerminal.getExtratermCookieValue()
  + [EXTRATERM_COOKIE_ENV]: newTerminal.getExtratermCookieValue(),
  + "COLORTERM": "truecolor", // Advertise that we support 24bit color
  };
  const pty = this._ptyIpcBridge.createPtyForTerminal(sessionUuid, extraEnv, newTerminal.getColumns(),
  newTerminal.getRows());
  