feat: add support for models API

[StevanFreeborn]

closes #26

• chore: update settings to format on save
• feat: add classes to model response to get model list endpoint
• feat: add model to represent paged request
• chore: stub out methods for retrieving list of models
• feat: implement ListAllModelsAsync and ListModelsAsync
• feat: implement GetModelAsync method
• tests: fix assertions
• fix: only allow afterId or beforeId to be set. not both at same time.
• docs: add examples for the model api to README.md
• chore: run dotnet format

[codecov]

Codecov Report

Attention: Patch coverage is 93.47826% with 6 lines in your changes missing coverage. Please review.

Project coverage is 98.23%. Comparing base (de326ab) to head (0b81bfc).
Report is 16 commits behind head on main.

Files with missing lines	Patch %	Lines
src/AnthropicClient/AnthropicApiClient.cs	88.46%	0 Missing and 6 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #30      +/-   ##
==========================================
- Coverage   98.57%   98.23%   -0.35%     
==========================================
  Files          67       70       +3     
  Lines        1264     1356      +92     
  Branches      103      119      +16     
==========================================
+ Hits         1246     1332      +86     
  Misses          5        5              
- Partials       13       19       +6     

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