Update Ruby Version to 3.1+ for Doc Site

[robyngit]

Our documentation site, which uses Jekyll, currently runs on Ruby 2.7. However, team members using Ubuntu 22.04 are encountering compatibility issues due to OpenSSL 3.0, which only supports Ruby versions 3.1 and above. Additionally, Ruby 2.7 has reached end-of-life, and Ruby 3.0 will soon follow, making an update necessary for future-proofing and maintaining security standards. According to this guide on upgrading Jekyll to Ruby 3.1, this "could be a relatively straightforward upgrade" since we don't appear make use of jekyll-assets.

Steps:

• Follow the guide to upgrade
• Upgrade and test dependencies
• Test building and serving the site on both linux and mac systems
• Update docs/README