Update README.md

[raynamharris]

removed the list of past workshops from the readme and and replaced it with a link to the workshop history page.

also replaced some html text with markdown text

[github-actions[bot]]

Reviewer Checklist

• [ ] spelling and grammar
• [ ] successful run of all installation and code chunks
• [ ] sufficient explanation and details for the tutorial content
• [ ] code syntax and naming convention
• [ ] adherence of tutorial format to style guide
• [ ] functional links (inter and intra)
• [ ] accessible hyperlink text