Add documentation deployment

This should hopefully take care of #2, where documentation is deployed
via GH Actions. I'll assign a custom domain later.

.github/workflows/docs_build.yml

@@ -0,0 +1,53 @@
+name: Publish Docs
+
+on:
+  push:
+    branches:
+    - root
+  workflow_dispatch:
+
+# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# Allow one concurrent deployment
+concurrency:
+  group: "pages"
+  cancel-in-progress: true
+
+jobs:
+  docs:
+    runs-on: macos-latest
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Set up Pages
+      uses: actions/configure-pages@v1
+    - name: Set up Swift
+      uses: fwal/setup-swift@v1
+      with:
+        swift-version: '6.0'
+    - name: Generate Docs
+      uses: fwcd/swift-docc-action@v1
+      with:
+        target: PuzzleKit
+        output: ./public
+        transform-for-static-hosting: 'true'
+        disable-indexing: 'true'
+    - name: Upload artifact
+      uses: actions/upload-pages-artifact@v1
+      with:
+        path: ./public
+
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: docs
+
+    steps:
+    - name: Deploy Docs
+      uses: actions/deploy-pages@v1