[Cashtab] Add fiat price value to tx history

Summary: Display USD value of BCHA transactions in transaction history

Test Plan: npm test. Can npm start and confirm appearance and css. This diff passes an existing variable to tx history and only renders the price if the inputs are valid.

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D9358