citybuilderjr sprint - basic mvp

[kfarr]

• [x] - add build using 3dstreet example
• [x] - add directories for files -- consider distinguishing between js for front-end app vs. js for gltf processing scripts
• [x] - add github pages
• [x] - test in quest, ensure migrated code from glitch is working
• [x] - add support for gltf placement instead of color voxel box
• [x] - create set-model-from-state component
• [x] - then look at how to use current html / state js add support for 2 gltf placements, switching like color
• [x] - currently image previews uses sprite component, instead we'll use a jpeg or png for each