Command-line option to list "other"/unidentifiable files

[dra27]

Using github-linguist 7.9.0 on a whole repository, it would be nice if the output of --breakdown included the files linguist couldn't identify the language of ("other") or even had an option explicitly to list them.

[pchaigno]

I'd welcome a pull request adding such an option.

[cbj4074]

Given that tools such as StyleCI require the "Pro" plan to analyze repositories that include more than one language -- and, apparently, Other counts as a second language -- it's frustrating not to be able to determine which files are categorized as such. I would likewise welcome such an option.