[TASK] Allow numbers in tags

[sabbelasichon]

Relates: #59

[ondrejmirtes]

What I need to see is a test for this change, I don't believe one-line regex changes like that :)

[sabbelasichon]

@ondrejmirtes: Total agree. At least the existing ones did not break. But what could be a real test case? I thought we are going to discuss this. I came up only with contrived examples. Because the "official" ones don´t have numbers in it. Our use case in somehow special and it is only relevant in the context of our custom Rector rules.

[ondrejmirtes]

Add another test in this file https://github.com/phpstan/phpdoc-parser/blob/master/tests/PHPStan/Parser/PhpDocParserTest.php, it has to fail without this regex modification.