Add left handed/right handed mode

[TheTeaCat]

https://bootcamp.uxdesign.cc/left-handedness-and-mobile-user-experience-a3728c72f880

Tl;dr we should make the new timer form on the bottom left aligned for right handed users, and right aligned for left handed users.

For left handed users, the header should also be reversed so the profile icon and title switch places.

We could also add a bonus "Australia mode" that flips the whole app upside down. That'd be pretty funny & easy to do.