[Feature] Options Chains From YFinance

[deeleeramone]

1. Why?:

   • Adds a free source to the derivatives.options.chains endpoint with just the core providers.

2. What? (1-3 sentences or a bullet point list):

   • obb.derivatives.options.chains(provider="yfinance")
   • Key data related to the underlying symbol is returned to extra["results_metadata"]. This info can be used as inputs for Greeks calculations, among other things.

3. Impact:

   • No changes to standard models or router components.

   • Better data coverage out-of-the-box.

4. Testing Done:

   • Unit/integration tests.

   • obb.derivatives.options.chains("^SPX", provider="yfinance")