Add LensSerialNumber

[mqudsi]

Found this while comparing the fields we need for some forensics. Exiftool supports it, fwiw.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.84%. Comparing base (383d0f6) to head (f384199).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #57   +/-   ##
=======================================
  Coverage   89.83%   89.84%           
=======================================
  Files          38       38           
  Lines        8393     8396    +3     
=======================================
+ Hits         7540     7543    +3     
  Misses        853      853           

Flag	Coverage Δ
nom-exif	89.84% <100.00%> (+<0.01%)	⬆️

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[mindeng]

Thanks for the contribution! Both CameraSerialNumber (#56) and LensSerialNumber (#57) are now included in nom-exif v3.5.0, just published to crates.io. Appreciate the help expanding tag coverage!