Added compression level to allow maximum compression

[NihalM99]

Issue #99 , if available:

Description of changes:

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[jwpage]

@NihalM99 thanks for implementing the fix to the issue, hopefully a maintainer can take a look (though I'm not expecting it - the repo hasn't seen a release since 2023)

[shaicoleman]

This forces the compression to the maximum level, which isn't desirable for everyone.
In my case the ZIP consists of already compressed files, so it will just slow things down.