Add a gotcha to the README

[haberdashPI]

As the title says

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a41c928) 95.97% compared to head (0698376) 95.97%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #37   +/-   ##
=======================================
  Coverage   95.97%   95.97%           
=======================================
  Files           1        1           
  Lines         273      273           
=======================================
  Hits          262      262           
  Misses         11       11           

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[SimonDanisch]

Thanks for adding this! If one thinks about it, it's obvious, but with the ability to hash deeply nested structs its easy to forget about it.

[SimonDanisch]

Ref: MakieOrg/Makie.jl#3394 (comment)