Add hydrate behavior to differences to React page

[marvinhagemeister]

In our case hydrate() is only meant to add event listeners, not patch the DOM.

[rschristian]

Do we still want to add this? AFAIK, we're now more lenient than React, e.g., we correct text leaf hydration mismatches, not fall over when encountering one.

Doing a bit of spring cleaning on our issues.