Docker image to automate dotnet builds

1. update dockerfile, and version number in package.json

2. build local version:

   npm run build

3. push new version to dockerhub:

   npm run push

4. tag and push again (optional but recommended):

   npm run publish

image: frontliners/dotnet-build

pipelines:
  default:
    - step:
        script:
          - /dotnet-build.sh