Add ability to dump output to a file

[altcointrading]

For the commandline tool.

Standard bash like > or 2>&1 doesn't work.

[zbayoff]

I would also like to see this feature.

[natke]

I tried the instructions here and the output went to a file: https://clementbm.github.io/github%20action/jekyll/link%20checking/2020/05/31/automatically-validate-links-on-jekyll-website.html

[gjtorikian]

I think this issue might be outdated. Regardless, I'm working on the next version of HTML Proofer and verified that the &> links.log redirection works.