This migrates our legacy Markdown to Restructured Text (RST). Now that
we have a website, we don't have to rely on rendering our docs on Gerrit
and GitHub, and can instead point at our webpage. This enables
1. Upgrading to a new Sphinx - our current version is 2 years old.
2. Using more sophisticated constructs like "note"
3. Adding custom CSS rules
Change-Id: I8153322efbcb307c1ca1ee3392b67f30f365f78c
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/40480
Reviewed-by: Armando Montanez <amontanez@google.com>
Commit-Queue: Keir Mierle <keir@google.com>
Pigweed-Auto-Submit: Keir Mierle <keir@google.com>
