Add React Unit Tests and Coverage Report

[amalnanavati]

Unit testing is a best practice for any software development, and React is no exception. This article and this has pointers on how to do unit tests and generate code coverage reports for React.

This issue encompasses the following TODOs:

• Implementing unit testing in this repository and adding unit tests for the existing code.
• Adding a CI check that runs unit tests.
• Adding a CI check that generates a code coverage report and (soft-)blocks merging if the unit tests' coverage over code has decreased.

[amalnanavati]

Sample configuration to add to the CI workflow when we have test cases to run:

- name: Run the tests
  working-directory: ./feedingwebapp
  run: npm test