NFCUI: Animated write tag screen

[sigboe]

@wizzomafizzo I can't currently test this, I need help testing it or else this will be postponed until I am able to test and have spare time, which I potentially don't know how long will be.

commit https://github.com/wizzomafizzo/mrext/pull/76/commits/fd7eaf93eb8adec8a8f29d93ba0ee92edb3f54e5 I meant to add a pause in handling SIGTERM while writing a tag. Which is potentially very useful, but I need it because I want to abuse nfc.sh by starting it and stopping it quite often, due to the next commit. What needs testing here is if this working.

commit https://github.com/wizzomafizzo/mrext/pull/76/commits/2750f543341e924f1a87046b288c1c01047bb274 Here is just some bash abuse, and I don't want to bash the face in of nfc.sh I want an animated screen the screen that asks the user to present an NFC tag for writing. Every time I update the animation I need to restart the write process. Hence wanting to ignore SIGTERM if write is happening. What needs testing is if 0.5s is enough time to enter the situation where we ignore SIGTERM. if not then we can reduce the animation speed