[Cashtab] Show an animated success modal for webapp-generated txs

Summary:
Cashtab current behavior is to instantly close the modal. In some "rapid fire" use cases, this can leave the user confused as to whether or not the tx actually broadcast.

Instead of automatically and instantly closing, show an animated success modal with the linked txid. The user can then click "OK" to close the extension or webapp tab.

Test Plan:
npm test, npm run extension, can try paybutton with the new extension

here's what the extension looks like after a successful tx:

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18547