feat: Start at offset from EXT-X-START

[mister-ben]

Starts at the offset specified in an EXT-X-START tag, which was currently parsed but not implemented.

Requirements Checklist

• [x] Feature implemented / Bug fixed
• [ ] If necessary, more likely in a feature request than a bug fix
  • [x] Unit Tests updated or fixed
  • [x] Docs/guides updated
  • [ ] Example created (starter template on JSBin)
• [ ] Reviewed by Two Core Contributors

[codecov[bot]]

Codecov Report

Merging #1389 (7421278) into main (2356c34) will increase coverage by 0.01%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1389      +/-   ##
==========================================
+ Coverage   85.45%   85.46%   +0.01%     
==========================================
  Files          40       40              
  Lines       10010    10017       +7     
  Branches     2317     2319       +2     
==========================================
+ Hits         8554     8561       +7     
  Misses       1456     1456              

Impacted Files	Coverage Δ
src/playlist-controller.js	95.20% <100.00%> (+0.04%)	:arrow_up:

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[adrums86]

I want to get this into the next release. Merging.