Added allow comments flag

[vtsykun]

Fixes #58.

In this PR has been added flag ALLOW_COMMENTS to allow ignore the comments.

Example usage:

$parser = new JsonParser();
$data = $parser->parse($content, JsonParser::ALLOW_COMMENTS);

Without this flag, JSON validation works as before, so there are not BC break here.

[vtsykun]

Seems a bug in phpstan

Line   src/Seld/JsonLint/Lexer.php                        
 ------ --------------------------------------------------- 
  116    Method Seld\JsonLint\Lexer::lex() should return    
         -1|1|4|6|8|10|11|14|[17](https://github.com/Seldaek/jsonlint/actions/runs/4088800683/jobs/7056125751#step:7:18)|[18](https://github.com/Seldaek/jsonlint/actions/runs/4088800683/jobs/7056125751#step:7:19)|21|22|23|24 but returns  
         -1|0|1|4|6|8|10|11|14|17|18|21|22|23|24|30.        
 ------ ---------------------------------------------------

phpstan/phpstan#8719

[Seldaek]

Thanks, looks good to me at first glance, will need some more time to review though

[Seldaek]

Thanks