Show supported runners on extension detail page

Follow up of https://github.com/cake-build/website/issues/580 and https://github.com/cake-build/website/issues/299. With the combination of Cake version the addin references and TFM we can decide with which runners it is compatible with based on the [supported platform table](https://cakebuild.net/docs/running-builds/runners/#supported-platforms).
An addin should be classified as compatible with a runner as soon as it targets a TFM, which is compatible with a runner. It shouldn't matter if an addin targets `netstandard2.0` or e.g. multi-targets `net641` and `netcoreapp3.0`.

This is of course only from a technical point of view, it's still possible that e.g. an addin targeting netstandard2.0 doesn't work on Cake .NET Tool on Linux. We should mention this in a tooltip.

Addin targeting .NET Standard 2.0:


Addin multi-targeting:


Add referencing latest Cake version but doesn't support all runners:


Addin referencing old Cake version and TFM:


Review the extension detail page and the supported platform table linked in the issue, along with follow-ups #580 and #299. Trace how the Cake version, referenced TFM, and runner compatibility are represented; done means compatible runners are shown for single- and multi-targeted addins, with a tooltip explaining that technical compatibility does not guarantee runtime support.

Written by the indexing model from the issue text.