Implement GitLab CI on Angular tests

This MR implements GitLab CI on Angular tests

How/Why has this been done:

• Added .gitlab.ci.yml with two (optional third) stages
  -Build: to build the application and install node modules
  -Lint: to run a node linter based on project preferences to ensure our code is homogeneous and not messy [OPTIONAL]
  -Test: to run Karma unit tests
• Modified karma.conf.js to include ChromeHeadless
• Docker image used is node:carbon which includes the stable version of Node
• In the testing phase, the dependencies for Puppeteer and ChromeHeadless are installed
• Unit tests run on ChromeHeadless, a headless version of Chrome which Karma launches and performs the tests on
  -Chrome Headless is run by Google's Puppeteer which was been added as a dependency -Chrome Headless was recommended after PhantomJS's development was ceased and it promises to be faster overall
  -Chrome Headless also allows e2e tests to be performed in the future if we decide to implement them
• Output is displayed in the terminal and prints a log to help us identify any issues
• A long list of flags have been added to help Chrome launch as minimally as possible and prevent issues

Current Status/Notes:

• Currently available tests are the auto-generated ones after component generation and test:
  -Creation of the component
• Unit tests are FAILING with some of the more common issues being: FIXED IN !97 (closed)
  -Missing imports on the TestBed (Routes, Pipes, Services, Components not being part of the module)#117 (closed)

On the bright side:

• Semester Pipe is the only project file that has proper tests running and passing successfully! Be sure to create tests for your code in a similar manner