I am curious how it works, technically speaking.
I already have this capability with password-store (pass), that works for Firefox, Chrome and Safari on destop and mobile.
pass - https://www.passwordstore.org (core program)
passff - https://github.com/jvenant/passff (firefox desktop)
passforios - https://mssun.github.io/passforios (ios w/firefox mobile)
qtpass - http://qtpass.org (osx, linux, windows)