[Images] Create conceptual article about multi stage building and its benefits

[erikaheidi]

This article would support the practice of multi-stage image building for language ecosystem images, so we can link from other sources and also share on social platforms. This is like the benefits of distroless, but explained in a slightly different way that focuses on the process of mixing images together in a Dockerfile to build an optimal final image.

[smythp]

This is a pretty good idea but maybe we could just make a long blurb instead of doing an article? Three paragraphs on multi-stage builds and we can blurb it on the language pages.