Add documentation for changing actions
Add documentation for changing actions

This new doc is the start of guidance for developers
(likely on 2nd line) making changes to the content
for the brexit dynamic list on behalf of content
editors.

https://trello.com/c/MPEdEhsJ/69-capturing-content-changes

alphagov/finder-frontend,alphagov/finder-frontend,alphagov/finder-frontend,alphagov/finder-frontend