REFACTOR: Address deprecation of putting `NODE_ENV=src` in `javascript/.env`

[pconrad]

REFACTORING GOAL:

Address the fact that it is deprecated to put this text into javascript/.env in order to allow import via absolute path

NODE_ENV=src

Deleting that file without replacing it with another approach will result in an error where the application fails to load with an error in javascript/src/index.js on the line that tries to do import App from "main/App";

So, instead, per Justin Vo's suggestion, replace with adding options into jsconfig.json as follows:

{
  "compilerOptions": {
    "baseUrl": "src"
  },
  "include": [
    "src"
  ]
}

Acceptance Criteria

• The file javascript/.env no longer in in the repo (if the only line in it was NODE_ENV=src). If something else is found, remove just that one line and leave the rest.
• All of the tests still pass
• The application still loads (do a simple manual "smoke test" on the home page on both localhost and heroku)