WARNING : ProjeQtOr in not compatible with PHP 7.4

Take care that ProjeQtOr is NOT compatible with PHP 7.4.x.

We plan to bring compatibility with ProjeQtOr 8.4.
Work is in progress and first tests area bit frightening.
Not about projeqtor code itself, that was fixed quite easily, but about external libraries, and more specifically html2pdf.
We had to bring some fixes on this library to have it work on PHP 7.4, but faced very slow PDF generation : exporting a ticket to PDF took 1mn and 45 second... compared to 9 seconds on PHP 7.3...
We'll investigate on that side, but one thing is sure : don't hurry to migrate to PHP 7.4...