videosink: Add options for JPEG and PNG encoders

[hansmi]

Expose the quality settings for the JPEG encoder and the compression
level of the PNG encoder via the Options structure.

Relates to #26.

[codecov-commenter]

Codecov Report

Merging #30 (e989a2f) into main (42ee855) will increase coverage by 0.1%.
The diff coverage is 92.3%.

@@           Coverage Diff           @@
##            main     #30     +/-   ##
=======================================
+ Coverage   61.2%   61.3%   +0.1%     
=======================================
  Files         53      53             
  Lines       6672    6690     +18     
=======================================
+ Hits        4085    4103     +18     
  Misses      2446    2446             
  Partials     141     141             

Impacted Files	Coverage Δ
videosink/handler.go	82.5% <0.0%> (ø)
videosink/display.go	90.0% <100.0%> (+2.5%)	⬆️
videosink/encoder.go	100.0% <100.0%> (ø)

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[maruel]

Thanks!