[ENHANCEMENTS] Allow for custom Whitelist/Blacklist result

[fyr77]

Is your feature request related to a problem? Please describe.
Currently, when using the whitelist or blacklist, HTTP status 403 is returned to anyone blocked.

Describe the solution you'd like
It would be nice to be able to return something different (such as a "sorry not available in your country") or redirect to another page or even a custom html page.

Describe alternatives you've considered

• Not use the blocklist: not an option for my use case
• Use another software such as caddy, which has this feature but no nice GUI like zoraxy.

[tobychui]

@fyr77 Actually I do have a template for the black / white list 403 respond body, which looks like this.

But I forgotten to include it into the go:embed. So that is why it falls back to a blank page with 403 HTTP Error.
I am working on it with the static web server function for customizable, I guess it will still take me a month or more to make it working (as I only work on this project in my free time).

In the mean time, you can modify this line in main.go and set this to true

development = false //Set this to false to use embedded web fs

and then modify the template (/web/forbidden.html) in the web folder for a temporary solution.