Enable `allowJs` and some other options in tsconfig (#18332)

* set `allowJs` to true in tsconfig. This allows TS to infer types from JS files

* added decorators

tsconfig.json

@@ -17,6 +17,9 @@
         "./enterprise/frontend/test/*"
       ]
     },
+    "allowJs": true,
+    "esModuleInterop": true,
+    "experimentalDecorators": true,
     "forceConsistentCasingInFileNames": true
   },
   "include": [