Build auto-generated markdown documentation for bbctl and its subcommands into the bbctl tool and keep them updated in the bbctl repo

Pitch

The Cobra library we use to build our bbctl CLI has a documentation generator module that can build markdown docs for every command and subcommand. How might we work that into the bbctl dev/build/release process, assuming anyone other than me finds it useful?

Here's an MR that adds an (untested) bbctl docgen command which created a dozen or so markdown files in my local clone (which I've also checked in, so you can see them).

• Example MR: !116 (closed)
• Example docs in the browser: root doc here, click around to read the subcommand docs as well

TODO

Design and integrate a more sustainable solution based around this cobra documentation generator module.