[Cashtab] Setup NFToa Icon

Summary: Add a reusable NFToa Icon React component based on nftoa.svg to represent NFToa brand identity within the Cashtab UI.

Test Plan:
Preview and check — this is an initial setup for the NFToa icon component. Further functional testing will be included in the
upcoming “NFToa Protocol ID integration” diff.

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, Fabien, bytesofman

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, Fabien

Subscribers: bytesofman, Fabien, nftoa

Differential Revision: https://reviews.bitcoinabc.org/D18784