Group k6 extensions by tiers

[imiric]

Currently all k6 extensions are listed together, and it's not clear which ones are officially maintained by Grafana, which ones are maintained by community developers, and perhaps more importantly, which ones are up-to-date with the latest k6 version. Having this information would allow users to determine which extensions are trusted and well maintained.

I think we should do two things (this might make sense as separate issues, let me know):

• Just like we have categories, add another group criteria to indicate ownership. For example, I think we should follow Packer's plugin tier system for this:

  

• Add yet another group criteria to indicate which versions of k6 the extension can be successfully built and run. We could relatively easily automate this, both the building and categorizing.

  As the extension ecosystem grows, the k6 team can't be expected to keep them all up-to-date with each possibly breaking k6 change. So it would be good to showcase the supported k6 version(s) directly on the extensions page.

[javaducky]

Just adding a note here that an internal design is currently being created for the website to utilize tiers.

[javaducky]

See #1113