[FEATURE] Setup CI/CD - GitHub Actions

[AVS1508]

Overview

Add GitHub Actions to streamline the continuous deployment and integrations.

1. Add a GitHub Action to build and test the React application before every merge into main branch, i.e. run when a PR is created that targets merging into the main branch. Reference: https://levelup.gitconnected.com/strengthen-a-react-application-with-github-and-github-actions-62977a781b37
2. Add a GitHub Action to automatically deploy Firebase Cloud Functions after every merge into main branch where a change in the functions/ directory is observed, i.e. run when a PR is merged into main branch which has some changes in the functions/ directory. Reference: https://davelms.medium.com/deploy-firebase-functions-using-github-actions-7dbafbd4df77