[Cashtab] CreateTokenForm to typescript

Summary: As prep for supporting other token types in Cashtab (ALP, mint vault), convert CreateTokenForm to ts

Test Plan:
npm test

I also created a token with icon and confirmed it worked as usual, since this is not covered by integration tests (which can't currently handle image manipulation)

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D17191