Replace packages/html2txt with Composer package
There is a html2txt package on Packagist, which is an updated version of the same class we have in the packages
repo, but updated for PHP8, includes tests, and assumes UTF-8 encoding is available in mail clients (e.g not changing ©
to (c)
). It also handles some less usual cases that the current class doesn't.
If we don't do this, we would at least want to pull in the updated class from Roundcube.