Escape all punctuation chars in markdown output

[aduh95]

Refs: nodejs/node#38522 (comment)

Ideally we would support backtick strings in commit message (as GitHub web UI now does), but a quicker fix is to escape them for now.

[rvagg]

Pretty big change, see the failed tests, 1\.2\.3 version numbers, \-\-blah flags, \#foo, etc.
Do a diff on the nodejs/node changelog with what this makes, it's going to make it much harder to human-read the raw markdown. I don't know if I'm +1 on this, escaping things like . and - are a bit much. Just because the markdown spec suggests that these can be escaped doesn't mean they should be. I'd recommend just escaping what's problematic. If you're suggesting escaping backticks, then escape backticks. But also be aware that these have been intentionally unescaped because it looks much nicer to have <code> blocks within the rendered commit messages and commit authors have been using it as such.
IMO the solution you're looking for is to find a regex that skips escaping inside each set of backticks.