Fix PHP8.3 support

[tzi]

[achanizbekovidnow]

Please merge the php8.3 fix to the master

[sc0ttdav3y]

HI @tzi!

While working on your PHP 8.3 maintenance branch, would you mind also looking at the PHP 8.3 deprecation notices in the current release? I get these notices with 2.3.1 under PHP 8.3.

 [PHP Decprecated] Creation of dynamic property Markdownify\ConverterExtra::$tableLookaheadHeader is deprecated in /vendor/pixel418/markdownify/src/ConverterExtra.php:87
 [PHP Decprecated] Creation of dynamic property Markdownify\ConverterExtra::$tdSubstitute is deprecated in /vendor/pixel418/markdownify/src/ConverterExtra.php:96
[PHP Decprecated] Creation of dynamic property Markdownify\ConverterExtra::$tableLookaheadBody is deprecated in /vendor/pixel418/markdownify/src/ConverterExtra.php:98

A quick look and it seems ConverterExtra potentially needs three variables declared:

private string $tableLookaheadHeader;
private string $tdSubstitute;
private string $tableLookaheadBody

I see this has been open for a while, so let me know if you need help to conclude it.

Cheers, Scott

[sc0ttdav3y]

Update: I've created a fresh PR https://github.com/Elephant418/Markdownify/pull/49 that incorporates this PR and my additional PHP 8.3 deprecation fixes.