Add polyfills for es2017, es2018, es2019

Fixes #100

server/server.js

@@ -149,6 +149,9 @@ function handleRequest(request, response) {
 					'es5': { flags: ['gated'] },
 					'es6': { flags: ['gated'] },
 					'es7': { flags: ['gated'] },
+					'es2017': { flags: ['gated'] },
+					'es2018': { flags: ['gated'] },
+					'es2019': { flags: ['gated'] },
 					'performance.now': { flags: ['gated'] },
 				}
 			}).then(function (bundleString) {