Faster Jekyll 4 builds on GitHub Actions

github-pages.yml

name: Build and deploy Jekyll site to GitHub Pages

on:
  push:
    branches:
      - master

jobs:
  github-pages:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v2
      - name: Install
        uses: ruby/setup-ruby@v1
        with:
          ruby-version: 2.7
          bundler-cache: true
      - name: Build
        run: bundle exec jekyll build
      - name: Deploy
        uses: JamesIves/github-pages-deploy-action@4.1.4
        with:
          branch: gh-pages
          folder: _site