[lib] Added new 'sendEditMessage' action
Summary: Added new action to send edit messages.
Test Plan: Checked if the app still works. Other tests are in later diffs.
Reviewers: michal, inka, ginsu, ashoat
Reviewed By: ashoat
Subscribers: ashoat, tomek, atul
Differential Revision: https://phab.comm.dev/D7129