site: document a gotcha when using on: and bind: together

[mindrones]

Closes #4616

[pngwn]

We don't want to be adding 'gotcha' sections to the docs, and also I don't think this needs it's own example.

This isn't a gotcha, it is a feature that was implemented to solve a problem. I think we need to remove the example and add a 'pullout' in the docs explaining that directives that interact with DOM nodes are run in the order that they are defined. This gives you the flexibility to control the flow.

[Conduitry]

I agree with @pngwn. This should be explained as a feature (which it is), and not as a gotcha that we can't be bothered to do anything about.

I also don't think this warrants its own tutorial page.