Test `Writer` is compatible with other zip extractors.

[nhz2]

Adds tests that zip files created by Writer can be extracted by other programs.

Currently, I have tests for p7zip, bsdtar, the python standard library, and Info-ZIP if it is available.

This should help with testing #99 and #85 and other future changes to Writer

Also updates the julia compat to 1.6. This is needed to test with bsdtar using LibArchive_jll