Add Black-76 model support

[carlobortolan]

Implement Black-76 Model

Description

Implement the Black-76 Model for options pricing in the options module.

Tasks

• Create black_76.rs in the options directory.
• Implement the price function for:
  • European Options
• Update tests

References

• Black Model
• Greeks
• Price Calculation

Assignees

• @carlobortolan