Add custom URLs option for the UrlConfig config.yml attribute

[d1rtdart]

Issue:
Allowing the ability to provide a "list" of URLs would be helpful for automation purposes (eq. building C2 server via terraform/ansible). Having a way to provide custom URLs would be a nice feature add. Being a public project, the "resources/urls.txt" has a potential to be easily identified by defensive security tools - using it is a dice roll. The "wordlist" option is a nice alternative as it is random, however, if you're using automation, you need to know what those URLs are going to be for the automated setup of your redirector's web configuration. Those are the only two options currently available (that I am aware of).

Recommendation:
Propose adding an additional option for the "UrlConfig" setting such as "custom" and adding an additional option such as "CustomUrlList" that takes a standard yaml list (again, great for automating using things like jinja2) or empty list as default "[]".

Thank you!