Add Drush command for configuring PHPStan

[mglaman]

Fixes #343

[mglaman]

Instead of being used to dump phpstan.neon, could be a supplemental file that gets included into the phpstan.neon for drupal related items.

[ondrejmirtes]

You don’t need to use nette/neon to write the file, you can output it like a human would, by echoing tabs and newlines 😊

[mglaman]

You don’t need to use nette/neon to write the file, you can output it like a human would, by echoing tabs and newlines 😊

😅 Yeah, thinking back it's not that bad. Especially since it's just "is string or array?" But apparently it was too much for my end of day brain

[mglaman]

Fails due to Symfony v4 and v6 compat, see https://github.com/drush-ops/drush/pull/5108/files#diff-fcb54a74a331c6112bd5cf5e32f08a4d0a39f42c16833b899b4fac0339d453c7

Need to call \Drush\Preflight\Preflight::loadSymfonyCompatabilityAutoloader – Drush 11 only!