Quicktext is a Thunderbird extension, which has been created by Emil Hesslow. However, he was no longer able to update Quicktext or provide any kind of support. Thankfully he changed the license of Quicktext to MPL 2.0, so I could continue to update the extension and make it work with the most recent version of Thunderbird.
This branch holds proof-of-concept code created by John Bieling. The goal was to show that composer manipulations can be implemented as a pure WebExtensions.