Guidelines how to add (and test) patterns for undetected trackers

[philipp-classen]

Currently, we lack documentation how to create patterns for undetected trackers. The best that we have are to point to examples. For instance, Cloudflare Insights (PR: https://github.com/ghostery/trackerdb/pull/92) was recently added. In general, coming up and testing the patterns rules can be a challenge though.

It would help if had guideline how to systematically create patterns and also how to test them in the Ghostery Extension.