Workshop material after a bit of clean-up

• Added the Quarto skin to create a webpage: _quarto.yml, .github/workflow/quarto_publish.yml
• Cleaned up the participants md's slightly so they can be built into Quarto website: made sure top level was # and no other # appeared in the markdown file.
• Did some minor clean-up on our Readme.md and split into two with top becoming index.qmd and agenda becoming schedule.md
• Added to described what the teams did teamwork.md.