Require the directoryOrFile argument when not piping into to stdin

[belav]

The --check option is not longer reporting missing files when used inside of a github action.

This was most likely caused by the changes for #282
Going back to 0.9.4, the current github action will fail a build for unformatted files.
As of 0.9.8 it definitely does not.
#282 came out in 0.9.6

After resolving this bug, also add a step to the ValidatePR that tests --check to ensure we don't break this again.

[belav]

When introducing the ability to read from stdin, a bug was introduced that caused --check to not work when run inside a github action.
One fix for this is requiring that directoryOrFile is supplied if not piping to stdin.
CSharpier can then read from stdin if stdin is redirected and directoryOrFile is not supplied. During a github action, stdin is redirected.
CSharpier will now fail to run if directoryOrFile is not supplied, which is a breaking change.