docs: 📝 update landing page of website (#34)

## Description

I mostly copied and pasted over from the other courses. It isn't
finished, since we need the Challenge and Need section filled out
eventually.

## Reviewer Focus

This PR needs a bit of a review. 

## Checklist

- [x] Ran spell-check
- [x] Formatted Markdown
- [ ] Rendered website locally

index.qmd

@@ -1,3 +1,46 @@
 # Welcome!
 
 {{< include includes/_wip.qmd >}}
+
+BACKGROUND: CHALLENGE
+
+BACKGROUND: NEED
+
+This course is designed to address these issues. We use a variety of
+learning activities like code-along sessions (instructor and learner
+coding together), reading activities, discussions, a few presentations,
+hands-on exercises, as well as a final group project. This website
+contains all of the material for the course, from reading material to
+exercises to images. It is structured as a book, with "chapters" as
+lessons, given in order of appearance. We make heavy use of the website
+throughout the course where code-along sessions follow the material on
+the website nearly exactly (with slight modifications for time or more
+detailed explanations).
+
+The course material was created using [Quarto](https://quarto.org/) to
+write the lessons and create the book format,
+[GitHub](https://github.com/) to host the [Git](https://git-scm.com/)
+repository of the material, and [GitHub
+Actions](https://github.com/features/actions) with
+[Netlify](https://www.netlify.com/) to create and host the website. The
+original source material for this course is found on the
+[`cog-flow-intro`](https://github.com/rostools/cog-flow-intro) GitHub
+repository.
+
+Want to contribute to this course? Check out the
+[README](https://github.com/rostools/cog-flow-intro/blob/main/README.md)
+file as well as the
+[CONTRIBUTING](https://github.com/rostools/cog-flow-intro/blob/main/CONTRIBUTING.md)
+file on the GitHub repository for more details. The main way to
+contribute is by using [GitHub](https://github.com/) and creating a [new
+Issue](https://github.com/rostools/cog-flow-intro/issues/new) to make
+comments and give feedback for the material.
+
+## Re-use and licensing {#licensing}
+
+<a rel="license" href="http://creativecommons.org/licenses/by/4.0/"><img src="https://i.creativecommons.org/l/by/4.0/80x15.png" alt="Creative Commons License" style="border-width:0"/></a>
+
+The course is licensed under the [Creative Commons Attribution 4.0
+International License](https://creativecommons.org/licenses/by/4.0/) so
+the material can be used, re-used, and modified, as long as there is
+attribution to this source.