Add a rating to extensions based on how well they follow best-practices

[pascalberger]

We currently list all addins. Some of them very outdated. We should either define a minimum version which they need to be compatible with or mark outdated addins clearly as outdated.

Suggested criterias for rating:

• Supports latest Cake version (Builds against recommended Cake version or newer) / Weight 10
• Works with all runners (Targets recommended .NET version or multi-targets) / Weight 9
• Has cake-contrib as co-owner / Weight 9
• Has alias category set / Weight 8
• Contains XML documentation / Weight 7
• Is hosted in cake-contrib org / Weight 5
• Has repository metadata / Weight 3
• Has license metadata / Weight 1
• Has icon embedded / Weight 1

Out of scope:

• Works cross platform (partially this is handled by target .NET version, but we can't rate if implementation works cross-platform)

[pascalberger]

Idea of @Jericho: Create some score for rating the quality of an addin based on the different things addin discoverer already analysis. This score could be written into extension yml files and then be visualized on addin list / detail page.