Babylon.js garment spikes

• Spike 1 · Brush paint on the tee
• Spike 2 · Place images on the tee
• Garment picker (the front end)

Both write into the tee's UV layout, which is the real-scale print pattern, so "Export print PNG" is the print file. Add ?res=4096 for print-resolution layers. Notes are in NOTES.md.