DOC: Provide example for scanning Containers with Sonatype Lifecycle

[jammsen]

Hello.

first of thanks for the work.

Now to the Feature-Request/Update-Request of the readme.md: I can see there is a segment in the readme,md thats named "Example Usage", sadly this covers only 1 example, namely "Maven Build". Please provide a current Docker-Image example, that covers both types:

1. Scan a local image
2. Scan a remote in a docker.io registry