jQuery 3.5.1
htmLawed 1.2.5
PHPMailer 5.2.28

Close #367.

Set to Unix line endings in repo; the gitattributes file means they
will be converted to suit the user’s system.

And normalize some line endings

Now using PHPMailer 5.2.7 and its autoloader.
Moved to ‘vendor’ folder and deprecated old qa-class.* files.
Closes #6.