chore: actualize documentation

[sonicfromnewyoke]

Problem

README.md served as both project documentation and a complete API cookbook with 2k lines of inline code examples for every RPC and WebSocket method. This caused several issues:

• stale examples - code snippets used removed APIs (bin.NewDecoder, CommitmentRecent, GetParsedTransaction) and wrong types (PublicKey vs *PublicKey) that silently broke without anyone noticing
• missing coverage - 3 methods implemented in the codebase (BlockSubscribe, SlotsUpdatesSubscribe) or in the Solana RPC spec (GetStakeMinimumDelegation) were absent from documentation
• unmaintainable size - at ~3000 lines, the README was difficult to navigate and update, discouraging contributions

Summary of Changes

• fixed 4 bugs found during migration: bin.NewDecoder -> NewBinDecoder, CommitmentRecent -> CommitmentProcessed, Mint/VotePubkey pointer types, removed nonexistent GetParsedTransaction
• implemented GetStakeMinimumDelegation - new RPC client method + result type to match the Solana spec
• extracted all examples into testable Example* functions - rpc/example_test.go (52 methods) and rpc/ws/example_test.go (11 subscriptions) that compile-check on every go build and render on pkg.go.dev
• slimmed README from ~3k to ~865 lines - kept project overview, install, key usage patterns; replaced the method catalog with compact reference tables linking to pkg.go.dev