Closes: #96, Closes: #253, Closes: #256

OK, multiple changes here:

1. renames in package.json :) There was still cloudforge name
2. move docker files back to docker dir
3. better scripts in bin, including new test and cleanup and reuse them in GA flow
4. Better structure in GA flow, use version 2 of docker/build-push-action

• test-js no meaningful changes
• test-docker - just tests the build but no publish
• publish-docker - dependent on success of test-docker, and if used just once on job level
• run only on commit to master or PR to master (before it was for any commit anywhere)

5. index.ts in the root => more consistent addressing from npm scripts and docker file
6. Some docs on the new features. Ans also "CI check list" section as a reminder what to be checked if the CI flow is adjusted

CI flow tested on https://hub.docker.com/repository/docker/sbcgua/abaplint-backend-dev but leaves some room for potential mistake because of the refs change in last commit. But hopefully should work. See also https://github.com/sbcgua/abaplint-sci-server/runs/1205277789?check_suite_focus=true