* Add "reference" help topic
* Only print reference as a help topic
* fix for color fns, slightly generalize
* WIP for switching to markdown
* escape gt/lt
* minor
* higher wrap point
* detect terminal theme
* futz with angle brackets once more
* minor cleanup
* prepend parent commands
* rename help topic fns and add test
* Simplify reference help generation
- the `<...>` characters from command usage line are now preserved by enclosing the entire usage synopsis in a code span
- hard breaks in flag usage lines are preserved by enclosing flag usage in a code block
- TTY detection and Markdown rendering are now delayed until the user explicitly requests `gh help reference`
- `gh help reference` output is now pager-enabled
Co-authored-by: vilmibm <vilmibm@github.com>
Co-authored-by: vilmibm <vilmibm@neongrid.space>
Co-authored-by: Mislav Marohnić <mislav@github.com>
