Allow option to use dynamic properties for specific classes

[marcelthole]

Hey,
i have a special use case where i need to allow dynamic properties via __get and __set in a class.
But with the strict type handling this package will not allow this, because all parameters must be known already.

So i created this PR for discussion if this solution would be fine for you.
The next idea could also be to check for the #[\AllowDynamicProperties] class attribute - But this will takle a little bit other problem, where you don't need the __get and __set at all.

[marcelthole]

I have still one isse and need your help here. I would like to use also generics for this implementation

/**
 * @template TValue
 * @extends \ArrayAccess<string, TValue>
 */
interface DynamicProperties extends \ArrayAccess {
    /** @return list<string> */
    public function getAdditionalPropertyKeys(): array;
    /** @return TValue */
    public function __get(string $name): mixed;
    /** @param TValue $value */
    public function __set(string $name, mixed $value): void;
    public function __unset(string $name): void;
    public function __isset(string $name): bool;
}

No i also want to use this strict types here and to validate the given values. Currently this implementation use the given type and i can't find a way to get the implements (or extends if i wrap it in an abstract class) TValue - or is it easier to get the type from the __set method signature? But this is without the TValue also only mixed