add '?' to nullable method parameters

[shu-yusa]

Issue: #228

From PHP8.4, a parameter that has null as a default value has to be typed as a nullable type: https://www.php.net/manual/en/migration84.deprecated.php
This PR adds ? to the method parameters that take null as a default value.

[shu-yusa]

cc: @kelvinmo

[shu-yusa]

I just noticed the CI has the matrix for different PHP versions. Let me add 8.4 to the matrix.

[kelvinmo]

Please update line 54 of .github/workflows/ci.yml to also use version 8.4. You will find that there are a few more method signatures that need to be updated.

 ------ ---------------------------------------------------------------------------------------------------------- 
  Line   SimpleJWT/InvalidTokenException.php                                                                       
 ------ ---------------------------------------------------------------------------------------------------------- 
  :90    Deprecated in PHP 8.4: Parameter #3 $previous (Exception) is implicitly nullable via default value null.  
         🪪  parameter.implicitlyNullable                                                                          
 ------ ---------------------------------------------------------------------------------------------------------- 

 ------ -------------------------------------------------------------------------------------------------- 
  Line   SimpleJWT/JWT.php                                                                                 
 ------ -------------------------------------------------------------------------------------------------- 
  :99    Deprecated in PHP 8.4: Parameter #4 $kid (string) is implicitly nullable via default value null.  
         🪪  parameter.implicitlyNullable                                                                  
  :207   Deprecated in PHP 8.4: Parameter #4 $alg (string) is implicitly nullable via default value null.  
         🪪  parameter.implicitlyNullable                                                                  
 ------ -------------------------------------------------------------------------------------------------- 

 ------ ------------------------------------------------------------------------------------------------------- 
  Line   SimpleJWT/Keys/Key.php                                                                                 
 ------ ------------------------------------------------------------------------------------------------------- 
  :237   Deprecated in PHP 8.4: Parameter #1 $password (string) is implicitly nullable via default value null.  
         🪪  parameter.implicitlyNullable                                                                       
 ------ ------------------------------------------------------------------------------------------------------- 

 ------ ----------------------------------------------------------------------------------------------------- 
  Line   SimpleJWT/Keys/KeyFactory.php                                                                        
 ------ ----------------------------------------------------------------------------------------------------- 
  :106   Deprecated in PHP 8.4: Parameter #2 $format (string) is implicitly nullable via default value null.  
         🪪  parameter.implicitlyNullable                                                                     
 ------ ----------------------------------------------------------------------------------------------------- 

 ------ ------------------------------------------------------------------------------------------------------- 
  Line   SimpleJWT/Keys/KeySet.php                                                                              
 ------ ------------------------------------------------------------------------------------------------------- 
  :95    Deprecated in PHP 8.4: Parameter #1 $password (string) is implicitly nullable via default value null.  
         🪪  parameter.implicitlyNullable                                                                       
 ------ ------------------------------------------------------------------------------------------------------- 

 ------ ----------------------------------------------------------------------------------------------- 
  Line   SimpleJWT/Util/CBOR/DataItem.php                                                               
 ------ ----------------------------------------------------------------------------------------------- 
  :127   Deprecated in PHP 8.4: Parameter #3 $tag (int) is implicitly nullable via default value null.  
         🪪  parameter.implicitlyNullable                                                               
 ------ ----------------------------------------------------------------------------------------------- 

[shu-yusa]

thank you for the feedback! I fixed them

[kelvinmo]

💚 All backports created successfully

Status	Branch	Result
✅	1.0

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