[Groff] GroffHub

[John Gardner]

Hello everyone!

Over the last four months, I've been working on a TextMate-compatible
grammar <https://github.com/Alhadis/language-roff> to improve the
highlighting of Roff source on GitHub. I submitted my pull request
<https://github.com/github/linguist/pull/3126> earlier today, and the
effect on code readability is *very* visible. Examples are in the PR.

The grammar's highlighting can be tested using GitHub's Lightshow
<https://github-lightshow.herokuapp.com/?utf8=%E2%9C%93&scope=from-url&grammar_url=https%3A%2F%2Fgithub.com%2FAlhadis%2Flanguage-roff%2Fblob%2Fstatic%2Froff.json&grammar_text=&code_source=from-url&code_url=https%3A%2F%2Fgithub.com%2Frust-lang%2Frust%2Fblob%2Fmaster%2Fman%2Frustdoc.1&code=>.
It'd be great to hear some feedback from veterans on the highlighting
accuracy!

Cheers,
- John