Adds support for PHP 8. The following changes were necessary to get the builds running again:
Composer 2 is installed by default, this isn't compatible with some of your dependencies so I've instructed it to roll back to Composer 1.
Psalm 1.1.9 includes syntax which isn't compatible with older PHP versions, while 1.1.8 isn't able to install on PHP 8. I've split the difference by making it install different versions depending upon the PHP version.
There was a use of a deprecated function which meant that the Psalm check was failing.
Adds support for PHP 8. The following changes were necessary to get the builds running again: