doc/documentation

$FreeBSD$

If you plan on building a local copy of the FreeBSD documentation, or using
our toolchain in your own projects, please read the Documentation Primer at:

    https://docs.FreeBSD.org/en/books/fdp-primer/

for information about the tools and formatting languages we use.
Chapter 1 has a Quick Start section, and Chapter 2 covers the software
and related items in more detail.