Fix links in several docs

This fixes #153 (closed).

For checking links I used this tool. It seems that it would be nice to automate this check. Thoughts?

@jacobvosmaer-gitlab could you please advise me something regarding my failed pipeline? It terminated by timeout (3600 sec), but I can do nothing with it - gdk install takes more time. And in my case this verification is not really helpful - I've modified .md files only.

@amaslenn Thank you for this contribution! Pipeline is red because of a timeout.

It looks good to me! Let's merge it. /cc @jacobvosmaer-gitlab @axil

added documentation label

assigned to @grzesiek

mentioned in commit 7723cb29

merged

Thanks @grzesiek!

What about automation for this check (my first comment)? I would take it :) One more question, is there anything to do with this timeout and long running verification?

Tool looks nice. Not entirely in favor of a Node dependency, although it is a transitive dependency already (GDK depends on gitlab-rails depends on Node).

I should say: the idea of using a tool looks nice, have not looked at this particular one.

@axil is this something we could use for all gitlab docs? Link checks? I don't think this should be exclusive to GDK.

The downside of doing this in CI is that you can get transient build failures.

@jacobvosmaer-gitlab glad you asked :)

Actually, I have a PoC in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9509 that can be run on every project.

Tool I mentioned uses markdown-link-extractor, I think there is a ruby implementation of such (or similar) functionality, so this particular check can be quite lightweight.

@jacobvosmaer-gitlab what do you mean by "transient build failures"?