Combine example without trimming

A helpful use case to add to the documentation:

How to combine data with different offsets and produce a larger scale mosaic without trimming the image. For example, the final image would be the total size of all the offsets of the sub-images

Start by locating the ccdproc documentation section covering data combination and examples. Check how combining sub-images with different offsets behaves when trimming is avoided, then document a case that produces a mosaic sized to include all offsets. Done means the use case and expected larger output are clearly explained.

Written by the indexing model from the issue text.