Add redaction guide

- Kept the wording of "General Law" as that's how its referred to in the theme that I link to in this guide.
I tripped over 'shared' here, as my first thought was the Facebook sense. (I'd also put “General Law” in quotes here) Perhaps something like:

The “General Law” information is much harder to automatically redact. It is not as structured, and the information is unlikely to be unique.