chore: add Node.js 20 EOL notice, add Node 26 to test matrix

[jbottigliero]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.88%. Comparing base (72e3fa1) to head (d3345ee).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #823   +/-   ##
=======================================
  Coverage   95.88%   95.88%           
=======================================
  Files          90       90           
  Lines        1800     1800           
  Branches      282      296   +14     
=======================================
  Hits         1726     1726           
  Misses         73       73           
  Partials        1        1           

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