dev(narugo): add e621 support

[narugo1992]

from cheesechaser.datapool import E621NewestDataPool

pool = E621NewestDataPool()

# download e621 #2010000-2010300, to directory /data/e621
pool.batch_download_to_directory(
    resource_ids=range(2010000, 2010300),
    dst_dir='/data/e621',
    max_workers=12,
)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.55%. Comparing base (d87fa47) to head (9020fb5).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #12      +/-   ##
==========================================
+ Coverage   81.09%   82.55%   +1.46%     
==========================================
  Files          29       30       +1     
  Lines         984     1055      +71     
==========================================
+ Hits          798      871      +73     
+ Misses        186      184       -2     

Flag	Coverage Δ
unittests	82.55% <100.00%> (+1.46%)	⬆️

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