Auto-generate aztec-nr references

[jzaki]

Currently this is aztec-nr reference documentation is generated.

With Noir syntactically being closer to Rust, assess if tweaking cargo doc for Noir language is a more robust solution.

Potential breakdown of sub-tasks:

1. Test generating reference docs from a simple Noir program/library
   • Handle docs:start, docs:end too if required
2. Generate reference docs from aztec.nr libs
3. Stretch goal - ensure docs can render well within a docusaurus docs site. Eg Aztec-nr reference here