Very hopeful but.. some problems yet. Rated 3 out of 5 stars
First of all, Thank you for awesome extension.
However, It have two problems.
1) No put the signature in mail.
2) Can't write a mail contens because interference with Nostalgy(another extension) keboard shortcut. It is due to compose in new tab embeded all another extensions.
Solving suggestion: Open in new window without another extensions when I compose mail.
I hope, this extension grow up to main editor in thunderbird.