Add CI workflows (testing & linting)

[xenosf]

Add CI checks using GitHub Actions. These checks run for every PR and push to the main branch. All tests except basic linting and system testing run on windows, mac, ubuntu.

Checks:

• Linting: Uses eslint to perform basic static checks
  • NOTE I had to modify some of the existing code to comply with the linting output. May need to fix other code to pass tests before merging this PR
• Client: Automated snapshot/unit testing using Jest
• Server: Automated unit testing using Jest for each service
• System: Automated system/integration testing using Selenium WebDriver on Chrome and Firefox

Not all unit/integration/system test cases have been written yet, this PR mainly sets up the CI workflow