Add `Ronin::Vulns::XXE`

[postmodern]

Add a Ronin::Vulns::XXE class which tests for XXE. It should rely on a listener URL (or host and port) that would receive the XXE HTTP request. URLScanner.scan should also have a xxe: keyword argument which is disabled by default. If the xxe: keyword argument is given, it should be given a Hash of keyword arguments that are given to XXE#initialize, which includes the callback URL (or host and port).

Prior Art

• XXEinjector
• xxe-injection-payload-list
• xxer