[FEATURE] firebase auth for web extensions

[tombeckenham]

Issue to be solved

Currently the chrome extension uses the standard Firebase. This causes us problems in the build where we have to remove injected scripts when building in webpack.

Suggest A Solution

Move to Firebase auth for web extensions which is a new version of the library which will avoid the issues we have in webpack having to remove analytics etc. See https://firebase.google.com/docs/auth/web/chrome-extension