feat: update a user methods or access to the firebase-admin instance

[buesing]

Is your feature request related to a problem? Please describe.

I need to update a user object, specifically the password, to prepare for a test. Another test is changing the password, then setting it back to what it was before. If this test fails for some reason, the password is not changed back, so I need to programmatically set it to what it was before in the next test.

Describe the solution you'd like

It would be nice to be able to use the user management methods from firebase. I think this could be easily possible if there was a way to create custom commands that can use the firebase-admin instance from within the plugin.

[prescottprue]

Direct access to the firebase-admin instance from the browser (where custom commands are running) would be tricky - it should be easy enough to expose some methods for interacting with auth user though.