[dx] Allow external rules without getRuleDefinition() to make them easier to write

[TomasVotruba]

We use getRuleDefinition() internally to allow easy search in 400+ rules - https://getrector.com/find-rule

But for the community/private projects, it's been only burden that is filled with lorem ipsun.
This patch requires docs for us and our packages, but drops the requirements for community to make writing custom rules easier 👍

[samsonasik]

Ref patch on website rectorphp/getrector-com@e9dbf78

[TomasVotruba]

Thanks 👍

[samsonasik]

@TomasVotruba instead of commenting out, I think it is better to have default empty getRuleDefinition in AbstractRector, eg:

abstract class AbstractRector extends NodeVisitorAbstract implements RectorInterface
{
    public function getRuleDefinition(): RuleDefinition
    {
        return new RuleDefinition('', []);
    }
}

wdyt? It doesn't enforce user to create it, but can create if they want to :)

[samsonasik]

I create a PR for it:

• [DX] Add default empty definition with add getRuleDefinition() method on AbstractRector #6444