fix: audio description track doesn't have icon on Safari browser

[gjanblaszczyk]

On Firefox/Chrome browser the HLS stream that contains an audio track with a description show AD icon in the menu list.

However, The same stream on Safari doesn't have the AD icon.

Description

Safari without VHS (in native mode) creates an audio track with a kind attribute value equal to "description".
Unfortunately, video.js handles track kind attribute value equal to "main-desc" only.

Specific Changes proposed

Add support for kind: "description"

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Change has been verified in an actual browser (Chrome, Firefox, IE)
  • Unit Tests updated or fixed
  • Docs/guides updated
  • Example created (starter template on JSBin)
• Reviewed by Two Core Contributors

[codecov]

Codecov Report

Merging #8232 (de1cc2d) into main (d26780e) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main    #8232   +/-   ##
=======================================
  Coverage   82.31%   82.31%           
=======================================
  Files         112      112           
  Lines        7452     7452           
  Branches     1796     1796           
=======================================
  Hits         6134     6134           
  Misses       1318     1318           

Impacted Files	Coverage Δ
...-bar/audio-track-controls/audio-track-menu-item.js	3.03% <0.00%> (ø)

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[mister-ben]

Not sure why the mixed content in the legacy docs is flagged for this PR in particular, but it's unrelated to the change.