Add a check for "garbage" files in a wheel

[John T. Wodder II]

The check should fail whenever a wheel contains files like:

• Text editor swap files (.*.swp, *~, .#*, .*.un~(?), *.bak(?), others???)
• .DS_Store
• ._* & __MACOSX (AppleDouble)
• Thumbs.db
• .coverage*
• .mypy_cache/
• directories containing a CACHEDIR.TAG file
• others???

Such files should also be included in the default value for --package-omit.