serializer.go

Summary of changes
- Added new event fires to enhance user feedback during the login process.
- Corrected terminology in the documentation for clarity.

- Introduced new event emissions:
  - "second-factor-success" is triggered upon successful second-factor authentication to signal any handlers waiting for this event.
  - "digits-success" fires once the digits button is successfully activated, allowing further actions to be taken.

- Updated the comments in the code to state "digit control" instead of "digits control," improving the grammatical accuracy of the documentation within `openDigits()` method.