Fix #89. Make some of UI Events composed events

[hayatoito]

Reflect the conclusion of WICG/webcomponents#513.

Make the following events composed events:

• Focus Events: blur, focus, focusin, focusout
• Mouse Events: click, dblclick, mousedown, mouseenter, mouseleave,
  mousemove, mouseout, mouseover, mouseup
• Wheel Events: wheel
• Input Events: beforeinput, input
• Keyboard Events: keydown, keyup
• Composition Events: compositionstart, compositionupdate, compositionend

Other editorial fix: I replaced [[DOM4]] with [[DOM]] for consistency
because bikeshed complains as follows:

FATAL ERROR: The biblio refs [[DOM4]] and [[DOM]] are both aliases
of the same base reference [[WHATWG-DOM]]. Please choose one name and
use it consistently.

[hayatoito]

@garykac @RByers
I appreciate if you have a chance to review this PR.