docs: Add link to hosted course demo

[jswope00]

Add a a link to a hosted instance of the course at https://training.openedx.org for people to try the course without having to import it

[openedx-webhooks]

Thanks for the pull request, @jswope00! Please note that it may take us up to several weeks or months to complete a review and merge your PR.

Feel free to add as much of the following information to the ticket as you can:

• supporting documentation
• Open edX discussion forum threads
• timeline information ("this must be merged by XX date", and why that is)
• partner information ("this is a course on edx.org")
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Please let us know once your PR is ready for our review and all tests are green.

[jswope00]

@sarina can I merge my own pull requests or is protocol that someone else approves?

[sarina]

On most repos, someone reviews your changes and then lets you merge in the PR when you feel it's ready. I wouldn't say it's strictly necessary on this repo, but, it never hurts for someone else's eye to catch typos etc.

[mphilbrick211]

@sarina @jswope00 - can this be merged?

[openedx-webhooks]

@jswope00 🎉 Your pull request was merged! Please take a moment to answer a two question survey so we can improve your experience in the future.