Add extra php attribute to methods for 8+ Fixes #52

[janw-me]

These functions are giving notices on php 8+.
The fix is adding a extra php attribute to the methods: #[ReturnTypeWillChange]

There where a couple of difficulties. So I took a different approach.

1. Just using sed for a method couldn't target the function of a specific class. So I used php reflection.
2. I wanted to prevent adding multiple #[ReturnTypeWillChange] So I check if it's not already present.
   So when PHP 8.1: fix deprecation warnings WordPress/Requests#505 lands, this won't create duplicates.
3. I wanted to make sure the indenting was correct for the attribute.

Overall fun thing to include.

[szepeviktor]

Overall fun thing to include.

:)
Thank you!!

[szepeviktor]

I'm very-very happy for your PR.

What do you think about my commits?

[janw-me]

The changes all seem fine by me.
Seeing the speed you made these. It's obvious you are far more comfortable with these type of commands.

One small note, that doesn't need to be changed.
Reason I used [[:space:]] is (posix) compatibility.
I understand that is not a problem here.

[szepeviktor]

All right. I agree.

But Bash is "improved POSIX" :)

[szepeviktor]

While releasing v6.0.2

PHP Fatal error:  Uncaught TypeError: Argument 1 passed to class@anonymous::getInheritedTagsForParam() must be an instance of phpDocumentor\Reflection\DocBlock\Tags\Param, instance of phpDocumentor\Reflection\DocBlock\Tags\InvalidTag given, called in /home/viktor/src/php-stubs/wordpress-stubs/visitor.php on line 509 and defined in /home/viktor/src/php-stubs/wordpress-stubs/visitor.php:535
Stack trace:
#0 /home/viktor/src/php-stubs/wordpress-stubs/visitor.php(509): class@anonymous->getInheritedTagsForParam()
#1 /home/viktor/src/php-stubs/wordpress-stubs/visitor.php(467): class@anonymous->discoverInheritedArgs()
#2 /home/viktor/src/php-stubs/wordpress-stubs/visitor.php(360): class@anonymous->addTags()
#3 /home/viktor/src/php-stubs/wordpress-stubs/visitor.php(340): class@anonymous->postProcessNode()
#4 /home/viktor/src/php-stubs/wordpress-stubs/visitor.php(330): class@anonymous->postProcessNode()
#5 /home/viktor/src/php-stubs/wordpress-stubs/vendor/php-stubs/generator/src/Result.php(49): class@anonymous->getStubStmts()
#6 /home/v in /home/viktor/src/php-stubs/wordpress-stubs/visitor.php on line 535

Viktor must work!

[szepeviktor]

This error does not belong here.

[szepeviktor]

@janw-me I've added a check here. Some methods do not exist in earlier core releases.