This is a rewrite with the web extension API. The main changes for the user are
- one letter key short cuts are now forbidden, so instead of 'y' one has to use CTRL + 'q' and instead of Shift + 'y' one has to use CTRL + Shit + 'q'
- the data storage is moved from a sqlite database to the local storage mechanism, this means if you are upgrading your old training data is lost and you need to retrain. I consider this tolerable as the extension was dead for years.

Compatibility with Thunderbird 68

This does not work with TB31

fix variable name clash to make it work with 10.*

fix the js reference so that it works in 9.* and the file case sensitive file name to make it work on Linux

This version does not work with 9.0