Please add FSharpPlus and FSharpX packages to TestRunner

[martinfreedman]

These are probably the two most used and popular addons when coding in FSharp for adding code and data structures respectively. (Already requested FSharp.Data and Json packages in other just posted issue)

[ErikSchierboom]

Would you be willing to PR this?

[martinfreedman]

Sur, I will follow your work on the Json and Parsing packages issues and then PR this?

[ErikSchierboom]

You could even include those in the same PR I feel. See https://github.com/exercism/fsharp-test-runner/pull/69/files for an example on how to add a package.

[martinfreedman]

Thought you might suggest that. happy to do this will check later this week