feat: show spinner when bridge btn is called

[thomas779]

Add a frontend spinner that shows the tx is loading and then displays a confirmation (✅) or error (🚫) depending on whether the event listeners.

Note:

• the event listeners from feat: add event listeners for bridgeTokensBack() and bridgeNonFungibleTokensBack() #11 will need to be implemented beforehand.
• Block blocknative notifications to avoid duplicate information events.