Simplify examples

[vincentfretin]

This closes #325

• added a prettier config with no trailing comma, single quote to match what we had previously but increase to 120 characters per line to have the avatar template entities on single line like we discussed.
• removed the imgur images, plane, sky, lights, particles
• used the arches environment component in all examples
• included the schema hack like I did in the basic.html example
• added a cameraRig to all examples
• removed the github corner on all examples, I left it only on the index.html
• renamed camera-rig to cameraRig, and local-avatar to player in tracked-controllers example so this is the same like the other examples
• added an explicit "adapter: wseasyrtc" in the examples where the adapter wasn't defined