[documentation] Add link to GitLab Pages template

I'm submitting a ...

• bug/error report
• feature request

What is the current behaviour?

There are some Jekyll templates for creating GitLab Pages sites, but they are only accessible if you know to look for them.

What is the expected/preferred behaviour?

Link the beautiful Jekyll just-the-docs and basic Jekyll templates from the community gitlab pages.

What is the motivation / use case for changing the behaviour?

Improves accessibility and knowledge sharing

Other information

Be sure to include details on how to give feedback on the templates, i.e. as issues of MRs on the template repos themselves.