[e.cash] Add button and bip70 label to wallets page

Summary: Slightly changed the copy at the beginning and added a button to our wallet guide. Also added the BIP-70 label to wallets that support it.

Test Plan: Visit e.cash/wallets and check copy, scroll down and check labels. Click the "Wallet Guide" button to see if it leads to the blog post.

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D16679