add 'gokill' to similar projects in docs

Just discovered this project, which was created over a year ago:

 * https://k4lipso.github.io/gokill/index.html

They have some interesting sets of triggers and actions (what we call triggers). It's not just USB removal events. More robust.

 * https://k4lipso.github.io/gokill/

Author: maltfield

docs/attribution.rst

@@ -67,3 +67,4 @@ The reader may be interested to investigate the following similar projects:
  * `pam_party <https://github.com/x13a/pam-party>`_
  * `AirWatch <https://vandersecurity.com/airwatch>`_
  * `swiftGuard <https://github.com/Lennolium/swiftGuard>`_
+ * `gokill <https://github.com/k4lipso/gokill>`_