Add first name as a new field

[paulinebessoles]

Hi @ferblape! Happy new year 😁

Would you accept a contribution to add a field for the user first name?

[ferblape]

Yes, it'll make the module more complete. I still have to update and merge #6, which add a couple of new fields too

[paulinebessoles]

Thank you for your quick answer! I'll keep you updated when we have some time to send the new first name field.