Docker image should be built as part of CD

[samouri]

summary
Context: #1240 (comment)

The Docker-based AMP Optimizer currently relies on manual build/release.
We should integrate it with our CD system so that we publish new versions the same time we publish new npm packages.

[sebastianbenz]

I assume that only releases should be published? In that case, a NPM script which then gets called after publish here should be a good first step.