Feature request: warn when rule contains HTTPS but HTTPS proxying is disabled

This would have saved me hours today .

Steps to reproduce:

1. Start whistle proxy
2. visit localhost:8899
3. Ensure Settings > HTTPS > "Capture HTTPS" is unchecked
4. Add Whistle rule where the source is https:// (e.g. https://localhost:420 http://localhost:6969)
5. Try triggering rule

Of course, it won't work because Capture HTTPS is disabled.

Feature request: If Capture HTTPS is disabled, warn me if I have rules containing https://.

As you can guess, this request comes from personal experience of pain