Set Up Continuous Integration / Delivery for WebTerminal

[nikitaeverywhere]

Action plan:

• [ ] Set up build pipeline (GitHub actions)
• [ ] Integrate open-source InterSystems Docker image for tests
• [ ] Write back end tests
• [ ] Write front end basic tests
• [ ] (optional) Lock up master branch & set up continuous delivery through manual confirmation.
• [ ] (optional) Produce a "beta release" in a master pipeline which goes live immediately for those who participate in a beta program, while the "tested" release goes live with an authorized button click only and applies for everyone
• [ ] Write an article about the solution