🐛 [firebase_ui_auth] Need "show password" option

[graemep-nz]

Bug report

An option for show/hide the password is needed See https://github.com/firebase/flutterfire/issues/10431 for files etc.

password_input.dart and universal_text_form_field.dart in issue 10431 have possible code changes needed to get this.

A checkbox option would be nice as well. Some people might not recognize the purpose of the icon.

[philitell]

Yes please this would be great!

[lesnitsky]

Duplicate #56