Entire code change for app.js

[Dan-B12]

Major Change API has been changed from OpenAQ to IQAir

• As part of the change to the API I had to modify all fetch requests to fit the new API calls.
• App.js has been almost entirely rewritten to fit the new solution.
• Multiple functions have been created for fetching each part of the location data, including country, state and city.
• Function to retrieve the AQI data using country, state and city to fit the requirements for the API.
• Added event listeners to check the presence of elements on the html page, as we have two web pages for this web app solution to display the AQI score.