Add py.typed, small improvements

[wRAR]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.90%. Comparing base (5cfa541) to head (acbe4be).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #266   +/-   ##
=======================================
  Coverage   97.90%   97.90%           
=======================================
  Files          14       14           
  Lines        1817     1817           
  Branches      343      343           
=======================================
  Hits         1779     1779           
  Misses         16       16           
  Partials       22       22           

Files with missing lines	Coverage Δ
scrapy_zyte_api/_request_fingerprinter.py	98.91% <100.00%> (ø)
scrapy_zyte_api/_session.py	99.29% <100.00%> (ø)
scrapy_zyte_api/handler.py	96.13% <100.00%> (ø)
scrapy_zyte_api/providers.py	94.73% <100.00%> (ø)

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