Adds a [`workflow_dispatch`][1] GitHub Actions CI workflow
that performs an E2E Cypress rendering test with Applitools
integration.
If the APPLITOOLS_API_KEY secret is not set, this action fallsback to
just doing a normal E2E Cypress test without Applitools support.
[1]: https://docs.github.com/en/actions/managing-workflow-runs/manually-running-a-workflow
