Fetch external sources for paths to scan

### What is the feature?

An idea from [`lc/gau`](https://github.com/lc/gau) where you look for URLs from AlienVault's Open Threat Exchange, the Wayback Machine, Common Crawl, and URLScan (we can try to see if there are more) to scan.

### What is the use case?

This will improve the scan results in general, who wouldn't use it?
