Add GitHub Actions workflow for docs deployment

Introduced a CI workflow specifically for the 'docs' branch to automate documentation deployment to GitHub Pages. The workflow triggers on push and pull request events, ensuring that any updates to the 'docs' branch are properly deployed. This enhances the efficiency of documentation updates and ensures a more streamlined process.

.github/workflows/docs.yml

@@ -0,0 +1,35 @@
+name: Crystal CI
+
+on:
+  push:
+    branches: [docs]
+  pull_request:
+    branches: [docs]
+
+permissions:
+  contents: write
+  pages: write
+  id-token: write
+
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  docs:
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Pages
+        uses: actions/configure-pages@v5
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: "./docs"
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4