Updates to home page and RNA-Seq on Cavatica lesson

[s-canchi]

PR Checklist

• [ ] Release label added
• [ ] PR category label added
• [ ] PR mergeable
• [ ] Clean build logs
• [ ] Linked related issues
• [ ] Colorblindness test https://www.toptal.com/designers/colorfilter/

PR Description

Mid release update to fix broken image links as well as updates to home page reflecting latest content.

Preview link https://cfde-training-and-engagement--470.com.readthedocs.build/en/470/

Review format

direct edit or comments

Timeline

today!

[s-canchi]

Note to update the image links in wiki pages to point to stable after merge.