Adding an Intro to UNIX lesson

[raynamharris]

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

This PR adds documents for an Intro to UNIX lesson and also makes some minor changes to landing pages.

Preview link

https://cfde-training-and-engagement--501.com.readthedocs.build/en/501/

Review format

Comments and suggestions and edits welcome.

Timeline

Not quite ready. Needs a csv lesson and proof reading.

[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

[raynamharris]

some screen shots

updated training home page

UNIX home page

[raynamharris]

Delete this branch for now.... it has some conflicts with the home pages and it's incomplete. I'll reopen a PR later when the lesson is actually ready for review.