Support PHP 8.3

[adamziel]

#829

PHP 8.3 was just released recently, let's support it in Playground.

https://www.php.net/releases/8.3/en.php#:~:text=PHP%208.3%20is%20a%20major,Upgrade%20to%20PHP%208.3%20now!

Done is

• The web version of Playground offers PHP 8.3 in its version switcher
• The node version of Playground runs PHP 8.3 when PHP=8.3 env is specified