JavaScript: Raise target to es2017

This significantly boosts performance of async/await, as it compiles to the "native" async/await rather than the `__awaiter()` polyfill.

Author: knutwannheden

rewrite-javascript/rewrite/tsconfig.json

@@ -1,6 +1,6 @@
 {
   "compilerOptions": {
-    "target": "es2016",
+    "target": "es2017",
     "module": "Node16",
     "moduleResolution": "node16",
     "isolatedModules": true,