Fix a camel case bug

[hansl]

This fix adds a Middle state when the character is in the middle of the string, as camelCase should not lowercase those. This happens on short middle fragments of the string.

Add tests for it too.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.30%. Comparing base (6ddc2b4) to head (4b43927).
⚠️ Report is 480 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4352      +/-   ##
==========================================
+ Coverage   47.24%   50.30%   +3.05%     
==========================================
  Files         476      499      +23     
  Lines       46892    50288    +3396     
==========================================
+ Hits        22154    25296    +3142     
- Misses      24738    24992     +254     

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