Add custom environment for Racket Programming language

[pschmied]

Issue #, if available:

Description of changes:
Demonstrate adding a custom environment for the Racket programming language, including brief example notebook demonstrating plot outputs from Racket in SMSL.

Testing done:

Merge Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your pull request.

• [ x] I have read the CONTRIBUTING doc and adhered to the example notebook best practices
• [ x] I have updated any necessary documentation, including READMEs
• [ x] I have confirmed secret codes are not included in the example.
• [ x] I have tested my notebook(s) and ensured it runs end-to-end
• [ x] I have linted my notebook(s) and code using black-nb -l 100 {path}/{notebook-name}.ipynb

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[icoxfog417]

Dear @pschmied thank you for the great pull request to enable Racket language on Studio Lab!

• Could you please make .yml file rather than installing environment in Jupyter Notebook for convenient setup for others? Please refer diffusers style.
• Could you please change .org to .md for simplification?