Add a FAQ page

[AMDmi3]

I've got a bunch of question emails during this weekend, so it looks like it's time to add a FAQ to the site.
Common questions:

• My package is not showing up in Repology (project search) - note that source package names are preferred; may be merged into differently named project; check if repository is correctly updated; check that the data contains the package
• Package from some repo is not showing on the badge - see related, may need manual rule

[coolaj86]

• I'm a repository maintainer. How do I add my repository to repology?

[AkechiShiro]

Hi, I would like to also know the answer to the question of @coolaj86