fix reading encoded strings

[vsaase]

this is a proposal, may need some testing the standard DICOM encoding is ISO-IR 6, which I think is something like ASCII. More common I think is ISO-IR 100 when not otherwise specified. At the moment I only check for UTF-8, known as ISO-IR 192 in the DICOM standard. There may be some other encodings in common use?

[pieper]

@vsaase thanks for the contribution 👍

I'll admit that text encodings is not my area of expertise. Would it be possible to make some test examples?

I recently added some small amount of testing and an https://github.com/dcmjs-org/data repo to store bulk data as release assets. Probably we'll continue to evolve the testing architecture but at least for now this gives us at least a little structure. (Suggestions welcome!).