feat(camelCase/capitalize/kebabCase/lowerCase/snakeCase/startCase): improve return types

[D-Sketon]

Even though the type passes the test, I can't guarantee that it covers all boundary cases

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.57%. Comparing base (b3a04ef) to head (330f9fe).

Additional details and impacted files

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##             main     #313   +/-   ##
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  Coverage   99.57%   99.57%           
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  Files         143      143           
  Lines         937      937           
  Branches      223      223           
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  Hits          933      933           
  Misses          4        4           

[D-Sketon]

close https://github.com/toss/es-toolkit/issues/172

[raon0211]

Hello, thanks for your contribution to our library! While I understand the reason of providing exact types, I am not sure they are worth it, considering maintainability and readability of complex types. Let me think a little bit about whether or not to include complex types to our library.

[raon0211]

Hello, thanks for your contribution.

Since we value simplicity of the implementation, we decided not to merge complex types in our repository.

However, other types of contributions such as adding new functions would be really helpful for us. Looking forward to your next contribution.