Update SUMMARY.md file

[emlini]

Per discussion in the Documentation Working Group meeting (notes here) 11/2, @emlini will update the SUMMARY.md file to reflect new outline for Hypha Docs (see "Outline" tab on this Google Sheet for the initial proposed organization--open for editing as we move forward, if this turns out not to make sense).

The outline is organized by user type--the different kinds of folks who will interact with Hypha--and will contain "how-to" pages for specific tasks/actions those user types will want to create, in addition to having two "horizontal" level categories ("Reference/Index" and "Understand/Learn more") with general information of interest or applicable to multiple user types.

[emlini]

Complete! See updated SUMMARY.md file.