Add Firefox 80 for Android (#6659)
Add Firefox 80 for Android (#6659)

According to https://www.mozilla.org/en-US/firefox/android/80.0/releasenotes/,
Firefox 80 for Android is released at August 31, 2020.
chrisdavidmills/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,mdn/browser-compat-data