Containerize the Admin UI

Built a deployment pipeline that builds a container image every time a change is merged into the main branch of this repository.

1. In the pipeline (.gitlab-ci.yml) I have added a reference to /devops/osdu/containerize.yml. (This will need to be merged in after this MR).
2. Containerize.yml executes a pipeline to build a deployable image using npm, angular CLI and nginx as webserver.
3. Dockerfile.azure has the build definition of the image.

Please see the readme.md in this pull request for more information.

This is only tested on Azure, but it will be possible to adapt the same containerize.yml and/or dockerfile to work with other CSPs as needed.

I have also configured Container Registry cleanup policy according to the OSDU guidelines.