Migrate GitHub Pages deployment to official actions

[MaxGhenis]

Current State

This repository currently uses JamesIves/github-pages-deploy-action@releases/v3 for deploying documentation to GitHub Pages (as seen in .github/workflows/push.yaml).

Proposed Change

Migrate to the official GitHub Actions for Pages deployment:

• actions/configure-pages@v5
• actions/upload-pages-artifact@v3
• actions/deploy-pages@v4

Benefits

• Official GitHub support and maintenance
• Better integration with GitHub Pages settings
• Follows GitHub's recommended best practices
• More reliable and secure

Implementation

Follow the official guide: https://docs.github.com/en/pages/getting-started-with-github-pages/using-custom-workflows-with-github-pages

Example implementation: MaxGhenis/disutility-of-uncertainty#2

Required Changes

1. Add proper permissions to workflow:

permissions:
  contents: read
  pages: write
  id-token: write

2. Update deployment steps to use official actions
3. Change GitHub Pages source to "GitHub Actions" in repository settings

This would modernize the deployment pipeline and align with GitHub's current recommendations.