Add decoder support for pixel format BGRA & ARGB

[zyxar]

Description

This PR adds decoder support for pixel format BGRA & ARGB, and enables them in pkg avfoundation.

[codecov[bot]]

Codecov Report

Merging #315 (1ff2ff2) into master (3d3830f) will decrease coverage by 0.53%. The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #315      +/-   ##
==========================================
- Coverage   55.90%   55.37%   -0.54%     
==========================================
  Files          54       55       +1     
  Lines        2277     2299      +22     
==========================================
  Hits         1273     1273              
- Misses        903      925      +22     
  Partials      101      101              

Impacted Files	Coverage Δ
pkg/frame/decode.go	50.00% <ø> (ø)
pkg/frame/rgb.go	0.00% <0.00%> (ø)

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[edaniels]

HI @zyxar, do you still want to get this in?