docs/sitemap: add ccd howtos
BRANCH=none
TEST=link takes you to the howtos doc.
* [Case Closed Debugging Overview](./case_closed_debugging.md)
* [Google Security Chip Case Closed Debugging](./case_closed_debugging_cr50.md)
+* [Tutorials](./ccd_howtos.md)
## Fingerprint MCU (FPMCU)
