[Cashtab] Link to Cashtab token page instead of explorer for NFTs in a collection

Summary: Now that cashtab loads arbitrary tokenIds, this page is much more useful than the block explorer. will show more token info and agora offer is present.

Test Plan:
npm test

npm start and check out an NFT Collection page. Click a link from the collection and verify it loads that NFT in another tab.

e.g. test it from http://localhost:3000/#/token/b0fa72f22f501e63bd0448387c162141fdcf61cf8aa0b0a01956468f260a0bf8

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D17395