Add Bitcoin example to the Lit developer docs

[a1ttech]

Using the Yacht-Lit-SDK and related Bitcoin tooling, add an example to the Lit developer docs that demonstrates how you can use PKPs to send and receive Bitcoin. You should be using the Lit SDK V3 for this project.

Please submit a PR to add this work to the 'Integrations' section of the docs by creating a new category for Bitcoin: https://developer.litprotocol.com/v3/integrations/

Please keep in mind that the Lit network is still in testnet and storing assets with real world value IS NOT RECOMMENDED at this time.