This adds the ability to hide certain options from certain help texts.
`--complete` is always hidden, whereas `--help` and `--version` are
hidden from Markdown help text only.
Note that in all cases these three options are hidden from the short
usage line.
This set was hand-curated, guided by the questions:
- Does it have at least three options, i.e. is the help page
non-trivial?
- Is the program unusual, i.e. does listing it in Help or on
man.serenityos.org spread awareness?
- Is the program common, but we only implement a subset of 'common'
flags?
