Buffer archive bytes in the ZIP example

[nhz2]

As noted by @JakeZw in #1158 (comment)

The zip file example was not properly closing things.
And as noted in JuliaIO/ZipArchives.jl#90, using mmap might not always be ideal.

This PR changes the example to avoid using streaming or mmap and instead buffers everything in memory to keep things simple.

I can give a more complete example based on the code in https://github.com/JuliaIO/ZipArchives.jl/blob/v2.5.1/test/test_file-array.jl
But this can get more complicated.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.75%. Comparing base (a0335ff) to head (b2e1330).

Additional details and impacted files

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##             main    #1166   +/-   ##
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  Coverage   95.75%   95.75%           
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  Files           9        9           
  Lines        5489     5489           
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  Hits         5256     5256           
  Misses        233      233           

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[quinnj]

[Reviewed by AI] Scoped review of the example at 8cf0b96.

Both zip-writing variants round-trip correctly through the proposed ZipReader(read(...)) / zip_readentry path with ZipArchives 2.5.1, CSV main ff0c032, and Julia 1.12.6. The shell-mode line was run as run(...) in the script.

Current main already closes the archive file through open(mmap, "a.zip") and uses zip_readentry. The remaining change is the choice to buffer the compressed archive with read. Keep the memory note: this example holds the archive bytes and the uncompressed entry bytes. Please port that small change onto current docs; this PR currently has 154 changed files and merge conflicts. I did not test the full historical PR checkout.