Restore --language none behavior for pmd cpd to find duplicates in plain text and Markdown?

[pspinrad]

Is your feature request related to a problem? Please describe.

With an older version of pmd, I used to run pmd cpd with --language none for finding duplicate text in big directories of markdown files, for streamlining documentation. Super handy!
Latest version doesn't allow none and when I try to fool it by passing in other languages, like ruby with filenames all ending with .erb, in verbose mode I get <filename> matches no known language, ignoring for all files.

Describe the solution you'd like

Enable text or plaintext or none or similar as a language option, and have that setting skip any built-in smarts relating to specific languages.

Describe alternatives you've considered

If not above, I'd like to revert to an earlier version, but I lost track of the version I used to run...

Additional context

Thank you for your consideration.