Update to ESLint 9

[simonmarty]

Issue #, if available:

Description of changes: Update to ESLint 9 following the migration documentation.

Corrected the listed license on the npm package from ISC to MIT-0. We do not publish this package to npm.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (aa511bf) to head (6cff27d).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #267   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          160       160           
  Branches        40        38    -2     
=========================================
  Hits           160       160           

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