Add note about access-token endpoint to README

[frederikprijck]

Ensure to callout how to opt-out from the access-token endpoint.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.77%. Comparing base (77a5b0c) to head (a398b0a).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2020   +/-   ##
=======================================
  Coverage   74.77%   74.77%           
=======================================
  Files          21       21           
  Lines        1859     1859           
  Branches      288      288           
=======================================
  Hits         1390     1390           
  Misses        462      462           
  Partials        7        7           

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