TD-3: Add Cypress test environment

[brianzelip]

This PR is a proof of concept for testing with Cypress.

• creates a Node.js dependency
• adds Cypress
• provides tests for the edit and report issue links added via TD-1: Add edit page and report issue links to every page #187
• adds GitHub Action workflow for running the tests in CI on all pull requests

To run the tests locally (requires npm, jekyll, etc), start the jekyll server in one terminal, and in another run the tests:

# Run the following from the tech-docs root dir

# install cypress
npm install

# start jekyll dev server in one terminal
npm start

# run the tests once server is running from another terminal
npm test

This PR is intended to be rebased once #187 is merged.

[brianzelip]

Closed in favor of #190