Add CI, Docker, and auto releases

[poma]

It's more reliable to generate releases via CI rather than a local build.

I've added Github actions that will generate a release draft with zip file attached when a tag like v1.4.0 is pushed to the repository. It also generates and uploads release container to Docker hub.

Details:

• build is triggered on push to any branch and on pull requests
• at the moment build action only builds client, this is a good place to add tests and linter in the future
• release action is triggered only when a version tag is pushed
• release action will:
  • Build release zip file
  • Build and upload Docker container
  • Generate a Github release draft and attach release zip to it

Before merging:
To publish to Docker hub, it requires DOCKER_USERNAME and DOCKER_TOKEN to be set up. Just create account on docker hub, generate an access token, and then add 2 secrets in your repository settings.

I've also added build status shields to readme, and included package-lock.json into release (it's highly recommended to do so, and also use npm ci to install packages on users machine)

You can see CI in action in my fork poma/assistant-relay and pushed images on Docker hub