Feature/node express okta setup

[kayla-himmel]

• added node and express to build the project
• added .env file for okta secrets
• refactored locations of assets and main logic (now in public folder under the assets folder and main.js file)
• added node/express logic to existing index.js file

Note: The authentication will need some refactoring still, but I'd love to get your feedback so far and especially to see if you can view the Okta auth screen (and successfully navigate it to get to the page content) after the note I sent you in Slack are addressed on your local. Thanks!