fix the capitalization of "sandbox" in .gitignore
fix the capitalization of "sandbox" in .gitignore

BabylonJS/Babylon.js,RaananW/Babylon.js,RaananW/Babylon.js,sebavan/Babylon.js,BabylonJS/Babylon.js,sebavan/Babylon.js,BabylonJS/Babylon.js,RaananW/Babylon.js,sebavan/Babylon.js