Publish docs to GitHub Pages

If all goes according to plan, this should build the docs page and
deploy it to GH Pages every time I push to `main`.

.github/workflows/docs.yml

@@ -0,0 +1,29 @@
+name: Docs Website
+
+on:
+  push: main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Build Documentation
+        run: nix build --print-build-logs '.#docs' --out-link docs
+      - name: Upload static files as artifact
+        id: deployment
+        uses: actions/upload-pages-artifact@v3 # or specific "vX.X.X" version tag for this action
+        with:
+          path: docs/
+
+  deploy:
+    runs-on: ubuntu-latest
+    permissions:
+      pages: write
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        uses: actions/deploy-pages@v4