Add support for alternative radars in JSON format

[mowday]

When you are using a Google Spreadsheet you can easily create multiple alternative radars in the same spreadsheet by creating new sheets. This is really useful when you want to convey different standpoints for different aspects.

This PR adds the same functionality in JSON format, by returning an object where they keys are the name of the alternative radars.

• [X] Added support for alternative radars in JSON
• [X] Added E2E tests to validate support including deeplinking
• [X] Added section the readme to update on the newly added support

[Drongerman]

Hi @andyflatt! Are you going to merge this?