add recovery example for mainnet XRP
add recovery example for mainnet XRP

Summary: https://bitgoinc.atlassian.net/browse/BG-4139

Reviewers: bigly, kevin

Reviewed By: kevin

Subscribers: ben

Differential Revision: https://phabricator.bitgo.com/D8233

BitGo/BitGoJS,BitGo/BitGoJS,BitGo/BitGoJS,BitGo/BitGoJS