Fix Ubuntu setup: add server.js, correct build instructions, add setup-ubuntu.sh#6

sriail with Copilot wants to merge 2 commits into

mainsriail/MCPE-WASM:mainfrom

copilot/update-ubuntu-setup-instructionssriail/MCPE-WASM:copilot/update-ubuntu-setup-instructionsCopy head branch name to clipboard