Synthetic Events: Document deviations from spec

[danburzo]

On the Synthetic Events page, I think there should be a Note whenever the React behavior deviates from the spec.

For example, onBlur bubbles. And, if I remember correctly from when I was studying rich-text editing, the onSelect event is also different from the selectDOM event?

Also, would it be overkill to put them in three-column tables, like this?

Synthetic Event	DOM Event	Notes
onBlur	blur	In contrast to the DOM event specification, onBlur will bubble.

[AlmeroSteyn]

This also happens for onFocus, so it should be added.

I think that, in the absence of focusin and focusout events, this is quite important to mention as these events feature strongly in making things accessible.