Add DICOM conformance statement

[cgorman]

This PR includes the DICOM conformance statement written by Markus and converted by me to markdown. Pandoc handled about 80% of it but there were some things I needed to manually tweak (e.g. the definition list).

[github-actions[bot]]

Visit the preview URL for this PR (updated for commit ea03982):

https://idc-external-006--pr158-doc-cg-conformance-s-n0zffsak.web.app

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[CPBridge]

Looks good to me. I'm slightly confused by the first table: what is the "Study Service" row and why is it blank?

[fedorov]

Comments from @dclunie:

• add source for the figures
• include original source for completeness

[fedorov]

Let's link it from the readme/front page.

[cgorman]

@fedorov @dclunie @CPBridge OK I think I addressed your comments/concerns, let me know if there's anything else.

[CPBridge]

I think we should just merge this, we can always tweak later