Add Repology datasource

[JamieMagee]

What would you like Renovate to be able to do?
Add support for the Repology API as a datasource

Describe the solution you'd like
Since the regex manager has been added, a lot of scenarios around Dockerfiles have been unlocked. With the existing datasources we can kind of support updating system packages, but support for Repology would be a safer way to do this.

Additionally, adding Repology could help in updating other package managers versions. See nixpkgs for an idea.

Describe alternatives you've considered

Additional context

[JamieMagee]

@ppmathis I can't assign this to you, but I marked this as "in progress"

[rarkins]

FYI issues can be assigned to anyone who comments on them

[ppmathis]

Let me comment here then - feel free to assign the issue to me afterwards 👍

Got a working implementation here, however the project grouping which Repology automatically applies is cumbersome, as e.g. pulseaudio-doc, pulseaudio-utils, libpulse0, ... are all grouped underneath a project called pulseaudio. The current API does not allow to search for a specific package name, so I've raised a request for that at repology/repology-rs#81

I will see if there is any update in the next few days, otherwise I'd push a version where dependencies have to be declared as <project>/<repository>/<package name> instead of just <repository>/<package name> as a first step.

[renovate-release]

🎉 This issue has been resolved in version 21.4.0 🎉

The release is available on:

• GitHub release
• 21.4.0

Your semantic-release bot 📦🚀