Suggestion: Support for multiple data sources and custom API URLs (Readsb support) #48

I would like to suggest an enhancement to support multiple ADS-B data sources by allowing users to configure a custom API URL and query format.
Proposed changes:

• Allow setting a custom base URL for the ADS-B data source.
• Add support for different API query formats and JSON processing:

• WebADSB: /lat/[lat]/lon/[lon]/dist/[dist] (current implementation)
• Readsb: /?circle=,,<radius_in_nmi> (newly requested)

Motivation:
This extension would allow the radar to connect directly to local/personal ADS-B receivers running Readsb software (such as those used in many DIY setups or feeders). This would make the project much more versatile for users who want to use their own local data instead of a centralized API.

Thank you for considering this request!