Editorial: Use GetOptionsObject from ECMA-262

[linusg]

Updating ecmarkup alongside biblio is not strictly necessary but comes with the nice side effect of adding dark mode to the rendered spec.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.91%. Comparing base (9291822) to head (4cbf8b4).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3262   +/-   ##
=======================================
  Coverage   97.91%   97.91%           
=======================================
  Files          22       22           
  Lines       10367    10367           
  Branches     1805     1805           
=======================================
  Hits        10151    10151           
  Misses        197      197           
  Partials       19       19           

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[ptomato]

Thanks!