add explicit refresh button for webapp installs

[jonknapp]

In iOS, you sometimes need to kill the application in order to get it to load the new data. There is probably a way to hook into the service worker picking up updates, but a faster solution would be an explicit reload button that shows up when the application is installed as a webapp.

• https://stackoverflow.com/questions/21125337/how-to-detect-if-web-app-running-standalone-on-chrome-mobile
• https://web.dev/get-installed-related-apps/