Add coverlet auto-detection

[Jsparham777]

Add ability to detect coverlet.MSBuild, coverlet.collector or display an error if neither package is found.

Disabling MSBuild in the settings did the trick. Now it's working. Is it possible to add some auto detection? And maybe output a warning if neither collector or MSBuild package is referenced.

Originally posted by @danielpalme in https://github.com/the-dext/RunCoverletReport/issues/1#issuecomment-650798778