Add WIP ADR for attachment handling for #1061

[aj-stein-gsa]

Committer Notes

Closes #1061.

All Submissions:

• Have you selected the correct base branch per Contributing guidance?
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• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you squashed any non-relevant commits and commit messages? [instructions]
• Have you added an explanation of what your changes do and why you'd like us to include them?
• If applicable, have all FedRAMP Documents Related to OSCAL Adoption affected by the changes in this issue have been updated.?
• If applicable, does this PR reference the issue it addresses and explain how it addresses the issue?

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[aj-stein-gsa]

This is not necessarily ready for review right right now, but it will be later in the afternoon and more importantly for others first thing Monday once I am on leave. So on that note, I will be changing status for my future aspirations now. 😄