Add FXMacroData release calendar example

[roberttidball]

Summary

• Adds FXMacroData release-calendar helper for using FXMacroData's public release-calendar endpoint in backtesting or strategy-risk workflows.
• Keeps the integration self-contained and avoids API-key requirements by using the public USD calendar example.

Validation

• Ran Python syntax checks for all added Python examples where applicable.
• Ran git diff --check for this repository.
• Live FXMacroData calendar smoke tested with the July 2026 USD sample window from companion Python examples.

Note: Go, Rust, .NET, Maven, and TypeScript toolchains were not available in the local desktop environment for deeper build checks.