Add linter to check for dead links?

[bjgill]

We're using this template for our technical documentation in GOV.UK Verify. One of the things we've found is that we slowly accumulated dead internal links due to content getting moved around.

To fix this, we've added a linter to catch new internal dead links, using html-proofer. It means that our docs will now not build if we introduce a new internal dead link.

Might this be something that would be useful to contribute upstream to the template?

[jonathanglassman]

It sounds extremely useful

[bjgill]

OK. I've raised #187 to implement.