consider adding org-wide workflow to lint whitespace

Some arguments in https://github.com/exercism/org-wide-files/pull/204#pullrequestreview-950940243.

And from e.g. https://www.kernel.org/doc/html/v4.10/process/coding-style.html
> Do not leave trailing whitespace at the ends of lines. Some editors with smart indentation will insert whitespace at the beginning of new lines as appropriate, so you can start typing the next line of code right away. However, some such editors do not remove the whitespace if you end up not putting a line of code there, such as if you leave a blank line. As a result, you end up with lines containing trailing whitespace.
>
>Git will warn you about patches that introduce trailing whitespace, and can optionally strip the trailing whitespace for you; however, if applying a series of patches, this may make later patches in the series fail by changing their context lines.

If we wanted to add whitespace linting, we could do it in `configlet lint`. But then we'd only lint whitespace in repos where `configlet lint` runs. So it seems an org-wide workflow is better.