Add code-style script to `composer.json`

[Sebbo94BY]

Since I'm using PHP 8.2 on my local machine, I had to set PHP_CS_FIXER_IGNORE_ENV=1, but it seems to work in general:

$ PHP_CS_FIXER_IGNORE_ENV=1 composer run code-style
> "vendor/bin/php-cs-fixer" fix --config .php-cs-fixer.php --diff
PHP needs to be a minimum version of PHP 7.4.0 and maximum version of PHP 8.1.*.
Current PHP version: 8.2.2.
Ignoring environment requirements because `PHP_CS_FIXER_IGNORE_ENV` is set. Execution may be unstable.
PHP needs to be a minimum version of PHP 7.4.0 and maximum version of PHP 8.1.*.
Current PHP version: 8.2.2.
Ignoring environment requirements because `PHP_CS_FIXER_IGNORE_ENV` is set. Execution may be unstable.

Fixed 0 of 52 files in 0.006 seconds, 14.000 MB memory used
Loaded config default from ".php-cs-fixer.php".
Using cache file "C:\Users\Sebastian\Downloads\ts3phpframework/php-cs-fixer.cache".

[ronindesign]

Nice, yes, this looks great!