feat(manpage): highlight options

[Eathox]

I felt these were missing from the current man support. I just kinda picked the first color that made sense to me, please correct me if there is a more suitable color in the themes.

Before:

After:

[injust]

Adding a screenshot of man ls, which has examples of -f|--foo and --foo=bar:

[sgoudham]

Superseded by #29