[WIP] Catalog XML examples for issue #139

[kscarf1]

[WIP] Created draft catalog XML examples in support of issue #139

Committer Notes

Created an initial draft of catalog XML examples embedded within the _catalogXML.md schema documentation file.

All Submissions:

• Have you followed the guidelines in our Contributing document?
• 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]

Changes to Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• [N/A] Have you written new tests for your core changes, as applicable?
• [N/A] Have you included examples of how to use your new feature(s)?

[iMichaela]