feat: rc-zip-tokio: Re-use cursor if it's at the right offset already

[fasterthanlime]

Closes #61

[codecov]

Codecov Report

Attention: Patch coverage is 91.30435% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 75.95%. Comparing base (a26f09d) to head (84dc0c6).

❗ Current head 84dc0c6 differs from pull request most recent head 597bdb2. Consider uploading reports for the commit 597bdb2 to get more accurate results

Files	Patch %	Lines
rc-zip-tokio/src/read_zip.rs	91.30%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #71      +/-   ##
==========================================
+ Coverage   75.81%   75.95%   +0.13%     
==========================================
  Files          25       25              
  Lines        2382     2404      +22     
==========================================
+ Hits         1806     1826      +20     
- Misses        576      578       +2     

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