docs: Update zip_writer documentation example

[romuald]

Replace the fixed size buffer example with a dynamic Vec

Since the buffer size was of fixed, size, the resulting zip file was always the same size, defeating the purpose of compression

fixes #430

[gemini-code-assist]

Summary of Changes

Hello @romuald, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request updates the zip_writer documentation example to use a dynamic Vec for its internal buffer instead of a fixed-size array. This change is crucial because the previous fixed-size buffer inadvertently limited the output zip file to a constant size, which undermined the demonstration of compression capabilities. By switching to a dynamic Vec, the example now accurately reflects how zip_writer handles varying output sizes and compression, and also shows how to retrieve the resulting bytes.

Highlights

• Documentation Example Update: The zip_writer documentation example now utilizes a dynamic Vec instead of a fixed-size buffer. This change rectifies an issue where the fixed-size buffer prevented the proper demonstration of compression, as the output zip file size was always constant.

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[gemini-code-assist]

Code Review

This pull request improves the ZipWriter documentation example by using a dynamic Vec instead of a fixed-size buffer, which is a great change. My review includes a minor suggestion to make the example code even more idiomatic by adjusting how the writer's ownership is handled. Overall, this is a good improvement to the documentation.

[gemini-code-assist]

This approach of passing a mutable reference to the Cursor is correct. However, an alternative and slightly more idiomatic approach would be to pass the Cursor by value, and then retrieve it from the result of zip.finish(). This makes the ownership transfer more explicit.

For example:

/// let writer = std::io::Cursor::new(Vec::new());
/// let mut zip = ZipWriter::new(writer);
/// // ... write files ...
/// let writer = zip.finish()?;
/// let zip_bytes = writer.into_inner();

This is just a suggestion for a cleaner style; your current implementation is perfectly fine.

[romuald]

This does not seems to be OK as the writer is not available afterwards because it has been moved