Make nullable parameter type hint explicitly nullable

[nimah79]

Is solves the following deprecation messages in PHP 8.4:

DEPRECATED  Morilog\Jalali\Jalalian::__construct(): Implicitly marking parameter $timezone as nullable is deprecated, the explicit nullable type must be used instead in vendor/morilog/jalali/src/Jalalian.php on line 47.

DEPRECATED  Morilog\Jalali\Jalalian::now(): Implicitly marking parameter $timeZone as nullable is deprecated, the explicit nullable type must be used instead in vendor/morilog/jalali/src/Jalalian.php on line 81.

DEPRECATED  Morilog\Jalali\Jalalian::fromFormat(): Implicitly marking parameter $timeZone as nullable is deprecated, the explicit nullable type must be used instead in vendor/morilog/jalali/src/Jalalian.php on line 105.

DEPRECATED  Morilog\Jalali\Jalalian::forge(): Implicitly marking parameter $timeZone as nullable is deprecated, the explicit nullable type must be used instead in vendor/morilog/jalali/src/Jalalian.php on line 110.

DEPRECATED  Morilog\Jalali\Jalalian::fromDateTime(): Implicitly marking parameter $timeZone as nullable is deprecated, the explicit nullable type must be used instead in vendor/morilog/jalali/src/Jalalian.php on line 120.

[morilog]

I accidently press sync with original repository and, all my changes have been gone. I reverted to v3.4.2 and your changes have been gone. please open a new merge request.