feat/custom functions

[KennyLewi]

added custom function:
IF: (condition, true_result, false_result)

also implemented better simulation error messages by replacing IDs with labels

closes #59
closes #53

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 0% with 82 lines in your changes missing coverage. Please review.
✅ Project coverage is 25.74%. Comparing base (3433210) to head (95b26ee).

Files with missing lines	Patch %	Lines
client/src/utils/displayEquationHelpers.ts	0.00%	38 Missing and 30 partials ⚠️
client/src/utils/equationValidationRegex.ts	0.00%	8 Missing ⚠️
client/src/actions/simulation.ts	0.00%	5 Missing and 1 partial ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##             main      #61      +/-   ##
==========================================
- Coverage   26.64%   25.74%   -0.90%     
==========================================
  Files          78       78              
  Lines        1888     1954      +66     
  Branches      323      349      +26     
==========================================
  Hits          503      503              
- Misses       1201     1242      +41     
- Partials      184      209      +25     

Flag	Coverage Δ
client	14.09% <0.00%> (-0.59%)	⬇️
server	87.98% <ø> (ø)

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[kellywsq03]

if you rename any entity to IF, the simulation fails
this is some silly edge case but we can consider preventing function names in labels