Add ability to specify root-path favicon file via commandline parameter in interactsh-server

[mikedesu]

Please describe your feature request:

My idea is straight-forward:

I want to pass a cmdline flag like -favicon to interactsh-server in order to specify a local file to serve at the root path for any interactsh-client instances I spin up.

Describe the use case of this feature:

I think it would be interesting to serve a giant local file (1gb+) to a target that makes HTTP requests.

interactsh-server -domain mydomain.site -favicon giantfile

So when I run a local client, asfahfefkhqfreq.mydomain.site/favicon.ico would return the giantfile.

This kind of attack could render some headless browsers vulnerable to DDOS or resource exhaustion.