Color image ISO speed for Capture

[hobbitsyfeet]

• Python Function called color_iso_speed since the iso "speed" (What Microsoft calls it) is currently only available for color images.
• Color iso speed property documentation is just copied from Microsoft's page
• This function must call Capture.color before requesting (like other color image functions)
• ISO speed is 0 when not available and raises "Cannot read iso from color_image" when 0 is returned.
• "Color image missed" when the image is not returned in pyk4a.cpp definition.
• Testing simply tests if capture.color_iso_speed is not None (initialized as none, 0 if error)
• Tested and works on live capture from the camera and not playback.

[codecov]

Codecov Report

Merging #176 (3ba32af) into develop (27af48d) will decrease coverage by 0.66%.
The diff coverage is 30.00%.

❗ Current head 3ba32af differs from pull request most recent head 8f5f801. Consider uploading reports for the commit 8f5f801 to get more accurate results

@@             Coverage Diff             @@
##           develop     #176      +/-   ##
===========================================
- Coverage    81.38%   80.71%   -0.67%     
===========================================
  Files           12       12              
  Lines          768      778      +10     
===========================================
+ Hits           625      628       +3     
- Misses         143      150       +7     

Impacted Files	Coverage Δ
pyk4a/capture.py	61.53% <30.00%> (-2.63%)	⬇️

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[lpasselin]

@hobbitsyfeet can you allow me to edit your fork? I made some minor changes.
Instructions here https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/allowing-changes-to-a-pull-request-branch-created-from-a-fork#enabling-repository-maintainer-permissions-on-existing-pull-requests