Update Zebra Book TOC
- [Inventory Tracking](dev/rfcs/0003-inventory-tracking.md)
- [Asynchronous Script Verification](dev/rfcs/0004-asynchronous-script-verification.md)
- [State Updates](dev/rfcs/0005-state-updates.md)
+ - [Contextual Difficulty Validation](dev/rfcs/0006-contextual-difficulty.md)
+ - [Zebra Client](dev/rfcs/0009-zebra-client.md)
+ - [V5 Transaction](dev/rfcs/0010-v5-transaction.md)
+ - [Async Rust in Zebra](dev/rfcs/0011-async-rust-in-zebra.md)
- [Diagrams](dev/diagrams.md)
- [Network Architecture](dev/diagrams/zebra-network.md)
- [zebra-checkpoints](dev/zebra-checkpoints.md)
