Chimera documentation

Portal built with mdBook. From the repo root:

mdbook build docs/
# output: docs/book/
AreaPath
Brand guidelines../brand/brand.md
ADRsadr/
RFCsrfc/
Guidesguides/
Nano-Kernel../crates/core-nano/
Nexus (scheduler-rt)../crates/scheduler-rt/
Releasing../RELEASING.md

See SUMMARY.md for the full table of contents (ADRs 0001–0024, RFCs 0001–0007, guides).