Minor cosmetic issues in explainer example code

[fordacious]

"Great example code in the explainer--relatively easy to follow. I noticed a potential issue in the second code example for Hand Interaction--checkInteraction runs once each frame, and thus when the hand enters the radius of the button in 3D space, the button will very rapidly toggle between pressed states 🙂. Not sure it matters from a pedagogical example though."

[Manishearth]

Yeah, perhaps we could add some debouncing code, or maybe a "// handle debounce here comment