add device registration

[sjonesdev]

we should add an option in the attendance form to register your device upon a successful attendance submission, meaning we could automatically detect when someone is registered and autofill their attendance info when visiting the attendance form page, maybe even auto-submitting. We would need to setup a database to store this data.

Alternatively, we could rely on the browser's localstorage api to have a client side autofill/submit feature