Create more obvious way to use component just for events

[donmccurdy]

Some devs may want to use this component to generate named events, but not to move around. Currently this is achieved with <a-entity keyboard-controls="enabled: false"></a-entity, which is not a good syntax. enabled: false should disable everything, including events, and there should be separate documented options like movementEnabled: true|false or eventsEnabled: true|false to achieve this.

[armthethinker]

This would be useful. I've been using KeyPress to handle my keyboard-tied events.