Improve discoverability of sample data for new contributors

[seancolsen]

It occurred to me today that new contributors don't seem to have any way of easily discovering our library data set. I'd like to make it more discoverable, and I'm leaning towards the following:

1. Rewrite the main README on the mathesar-data-playground repo as follows:
   • Cut most of the intro content, linking instead to the Mathesar repo
   • Add a section with clear, concise, imperative instructions for people who just want to load the sample data and move on to their next task with Mathesar. A newcomers should be able to go from landing on this README to having the latest recommended library data set loaded into their local Mathesar installation in under 5 minutes.
2. Add a "Sample Data" section to our README (after "Local Development") linking to the mathesar-data-playground repo.
3. Add a "Get sample data" step within our Contributor Guide (after "Get Mathesar running locally") linking to the mathesar-data-playground repo.

Does this seem okay @kgodey @mathemancer?

[kgodey]

That sounds fine as a documentation change, @seancolsen.

I think we should also figure out a quick path to loading the live demo data set into the main DB. This shouldn't be too hard because we already have logic for loading it into demo DBs in the mathesar codebase. It will involve some code in addition to documentation changes, so it should probably be tackled as a future improvement.

[github-actions]

This issue has not been updated in 90 days and is being marked as stale.

[hitenvidhani]

Attaching the referred message which contains steps here

[hitenvidhani]

Opened a PR to close this.
#3535