bitcoin info - updates for some BDP and Chaincode links

[satsie]

This PR adds links for some Bitcoin Development Project (BDP) stuff, as well as the Chaincode Labs ₿OSS program. To my delight, many of the links I planned to add as part of #1106 are already here!

• BTC Transcript Review (Buying & Earning BTC | Earning bitcoins) - Earn BTC for reviewing AI generated transcripts
• Decoding Bitcoin (Online & Offline Classes | Technical Online Classes) - Interactive course on bitcoin tech
• BTCdemy (Online & Offline Classes | Technical Online Classes) - Intro to Rust course with bitcoin based exercises
• Good First Issues (Technical Resources) - List of Good First Issues from vetted projects across the space
• Chaincode Labs ₿OSS program (Careers | Internships) - Part mentorship, part internship, part self guided course designed to take participants from zero to full time ₿OSS (bitcoin open source software) contributor

All 100% free and open source :)