React Build Errors with Optional Chaining.

If you are building your application with react and you are seeing the error:

"module parse failed: Unexpected token" 

due to the use of Optional Chaining in the object path ( e.g. process.env?.JEST_WORKER_ID ), see the example below:

To resolve the issue please add react-scripts version 4.0.3 to the devdependency of the package.json.

Also in the package.json broswerlist should add the following to the browserslist section:

"browserslist": [
   ">0.2%",
   "not dead",
   "not op_mini all"
]