Update Readme.md and method documentations

[gbarkhatov]

Re-write the README for the btc-staking-ts to reflect the latest manager and staking changes. The existing REAME content is designed for the low layer transaction.ts in which should still be valid and people who want to do their own staking tx can make use of it. We can relocate to a sub directory or child page etc.

Also keep in mind for the https://babylonlabsworkspace.slack.com/archives/C07DYV8TEDD/p1739093387002099?thread_ts=1738219349.709519&cid=C07DYV8TEDD