UI - Add list of currently available executors

[fivenp]

Describe the enhancement you'd like to see We want to list and show all the available executors Testkube currently supports and do some outbound links for each executor to help our users understand what the executors actually do. (Ideally we would have some quides and more content on our own for each executor – but for now we can maybe just link to the projects?)

https://www.figma.com/file/asfUPepLHtyutWWR0pNGfK/Testkube-V2?node-id=73%3A44260