Rated 5 out of 5 stars
HowTo for enabling this addon under 60.2.1 (probably it will work with other versions too):
1. Download addon as a *.xpi file
2. Open addon in any archive manager or use Midnight Commander to go into.
3. Edit file 'install.rdf': change field "<em:maxVersion>7.0</em:maxVersion>" to "<em:maxVersion>60.*</em:maxVersion>" (if you need another version - use this link to find a valid version https://addons.thunderbird.net/en-US/thunderbird/pages/appversions/)
4. Open Add-ons Manager, click on "gear" button and choose 'Install Add-on From File...'
5. Click 'Install', enjoy your life and say 'Thank you, dude from Russia'. =)