PluXml 5.8.7

[+] Move plugins cached css files to data folder #526 (bazooka07)
[+] Open static page from administration in a new tab #532 (bazooka07)
[+] i18n Occitan correction #535 (Mejans)
[+] PHPMailer update to 6.4.1 (P3ter)
FIX Comments no more displayed with PHP8 #529 (bazooka07)
FIX Revert .htaccess generation for plugins compatibility with url rewrite (P3ter)
FIX Wrong use of uasort() in pages and categories edition #530 (bazooka07)
FIX Display 404 error page when switching to a theme with a missing template #533 (bazooka07)
FIX Category creation can replace an existing category #534 (bazooka07)
FIX Minors CSS fixes (P3ter)