feat: lexer and parser for mutually exclusive choices in format strings

[Seddryck]

No description provided.

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 89.74359% with 8 lines in your changes missing coverage. Please review.

Project coverage is 91.48%. Comparing base (135b952) to head (cec318e).

Files with missing lines	Patch %	Lines
src/Chrononuensis.Core/Formats/Lexer.cs	88.05%	4 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #49      +/-   ##
==========================================
- Coverage   92.28%   91.48%   -0.80%     
==========================================
  Files          20       21       +1     
  Lines         285      329      +44     
  Branches       38       45       +7     
==========================================
+ Hits          263      301      +38     
- Misses          8       12       +4     
- Partials       14       16       +2     

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