date return type numeric-string for specfic formats

[kkmuffme]

https://psalm.dev/r/0264caa556

If the first argument of (gm)date matches ^[djNwzWmntLoyBgGhHisuvIZU]+$ then the return type should be numeric-string instead of string

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/0264caa556

<?php

$type = gmdate( 'H' );
/** @psalm-trace $type */;

Psalm output (using commit 2aaa577):

INFO: Trace - 4:26 - $type: string

INFO: UnusedVariable - 3:1 - $type is never referenced or the value is not used

[orklah]

This may be too complicated to put into a stub. A return type provider would do the trick though