[panel] Check if FQDN is an IP

[Linux123123]

Add's a regex check similar to email, to check if provided FQDN is an IP.

[Linux123123]

This is only panel, because it would require quite a bit more work on wings script.

[vilhelmprytz]

I just tried this locally and it still allows me to proceed with automatic Let's Encrypt. Without looking too much at the code, have you verified that this is working?

[Linux123123]

I just retested and that regex doesn't work that well. So I just added a much simpler ip checking with ip.

[vilhelmprytz]

This works a lot better now. Thanks, LGTM!