Add GitHub workflow for deploy

.github/workflows/main.yml

@@ -0,0 +1,33 @@
+name: Build and deploy
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: 3.2
+
+    - name: Install dependencies
+      run: |
+        bundle config path vendor/bundle
+        bundle install --jobs 4 --retry 3
+
+    - name: Compile
+      run: |
+        bundle exec rake compile:all
+
+    - name: Deploy to GitHub Pages
+      uses: peaceiris/actions-gh-pages@v3
+      with:
+        github_token: ${{ secrets.GITHUB_TOKEN }}
+        publish_dir: ./dist

Gemfile

@@ -1,5 +1,8 @@
 source "https://rubygems.org"
 
+# NOTE: Keep in sync with .github/workflows/main.yml.
+ruby "3.2.2"
+
 gem "rake"
 gem "webrick"
 gem "slim"

README.md

@@ -15,4 +15,6 @@ TODO: Run guard automatically via Devbox.
 
 ## Production
 
-Deployed via [GitHub Pages](https://pages.github.com/). Just push.
+Just push.
+
+Deployed via [GitHub Pages](https://pages.github.com/) and the workflow in `.github/workflows/main.yml`.

Rakefile

@@ -19,4 +19,7 @@ namespace :compile do
       puts "Compiled #{file} to CSS!"
     end
   end
+
+  desc "Compile Slim and Sass"
+  task :all => [ :slim, :sass ]
 end