message: refactor(background): check update every 20 days
diff: @@ -90,7 +90,7 @@ function onStartup (): void {
  storage.local.get<{ lastCheckUpdate: number }>('lastCheckUpdate')
  .then(({ lastCheckUpdate }) => {
  const today = Date.now()
  - if (!lastCheckUpdate || !(today - lastCheckUpdate < 7 * 24 * 60 * 60 * 1000)) {
  + if (!lastCheckUpdate || !(today - lastCheckUpdate < 20 * 24 * 60 * 60 * 1000)) {
  checkUpdate().then(({ info, isAvailable }) => {
  storage.local.set({ lastCheckUpdate: today })
  if (isAvailable) {
  