Add GitHub Actions workflow for Jekyll deployment

[allie0684]

This workflow builds and deploys a Jekyll site to GitHub Pages, with steps for checking out the code, setting up pages, building the site, and deploying it.

Why:

Closes:

What's being changed (if available, include any code snippets, screenshots, or gifs):

Check off the following:

• A subject matter expert (SME) has reviewed the technical accuracy of the content in this PR. In most cases, the author can be the SME. Open source contributions may require an SME review from GitHub staff.
• The changes in this PR meet the docs fundamentals that are required for all content.
• All CI checks are passing and the changes look good in the review environment.

[github-actions]

Thanks for submitting a PR to the GitHub Docs project!

In order to review and merge PRs most efficiently, we require that all PRs grant maintainer edit access before we review them. For information on how to do this, see the documentation.

[github-actions]

How to review these changes 👓

Thank you for your contribution. To review these changes, choose one of the following options:

• Spin up a codespace
• Set up a local development environment

A Hubber will need to deploy your changes internally to review.

Table of review links

Note: Please update the URL for your staging server or codespace.

This pull request contains code changes, so we will not generate a table of review links.

🤖 This comment is automatically generated.

[github-actions]

👋 Hey there spelunker. It looks like you've modified some files that we can't accept as contributions:

• .github/workflows/jekyll-gh-pages.yml

You'll need to revert all of the files you changed that match that list using GitHub Desktop or git checkout origin/main <file name>. Once you get those files reverted, we can continue with the review process.

The complete list of files we can't accept are:

• .devcontainer/**
• .github/**
• data/reusables/rai/**
• Dockerfile*
• src/**
• package*.json
• content/actions/how-tos/security-for-github-actions/security-hardening-your-deployments/**

We also can't accept contributions to files in the content directory with frontmatter type: rai or contentType: rai.