Add "harassment and abuse" to high-level threats

[npdoty]

This is connected to "intrusion" and the Intrusive behavior category, but it's probably distinct enough for a separate heading. This could include unwanted messages, showing disturbing images, spammy behavior, persistent contacts, etc.

[npdoty]

some blog posts on my own thinking about Web-specific issues and responses:
http://bcc.npdoty.name/Dealing-with-harassment-and-spam-on-the-Web
http://bcc.npdoty.name/May-there-be-shared-blocklists

[jyasskin]

This OurSA talk on Advocating for High Risk Groups introduced me to this topic, and we should make sure that the speakers there agree with whatever we write here.