Add test for DICOM in Dataset.from_images

[hotzenklotz]

Many medical datasets come in the standard DICOM format.

We are already using nibabel for NIFTI files. They claim limited support for DICOM.

Further reading:

• nibabel
• pydicom
• Medium Article

[jstriebel]

This should already be supported in Dataset.from_images via the pims imageio reader. We should add a test for this. Will then be solved via #825.