Enhance README with project details and repository links

[lauraporta]

Expanded project description and added details about two repositories.

[adamltyson]

GitHub seems to be having issues, it won't let me comment on the PR. I will leave comments here, rather than inline.

• I think the schematic should have a white background. I don't think it will show up well in dark mode when rendered on the org page.
• In the first sentance, I think that for consistency, each partner should link to the respective website, rather than two GitHub orgs and one website.
• I would remove the reference to NIU in the pipeline description. While we are leading this, we don't want to discourage others from getting involved if they wish.