Add GitHub Actions workflow to deploy playground to GitHub Pages (#14)

* Add GitHub Actions workflow to deploy playground to GitHub Pages
* Add Playground Example section to README.md

Author: Copilot

.github/workflows/deploy-playground.yml

@@ -0,0 +1,63 @@
+name: Deploy Playground
+
+on:
+  push:
+    branches: [master, main]
+
+# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# Allow only one concurrent deployment, skipping runs queued between the run in-progress and latest queued.
+# However, do NOT cancel in-progress runs as we want to allow these production deployments to complete.
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build UMD bundle
+        run: npm run build:umd
+
+      - name: Prepare playground files
+        run: |
+          mkdir -p _site/dist
+          cp samples/language-service-sample/index.html _site/
+          cp samples/language-service-sample/app.js _site/
+          cp samples/language-service-sample/styles.css _site/
+          cp dist/bundle.js _site/dist/
+
+      - name: Setup Pages
+        uses: actions/configure-pages@v5
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: '_site'
+
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4

README.md

@@ -55,6 +55,14 @@ Parser.evaluate('6 * x', { x: 7 }) // 42
 - **Object Construction** - Create objects and arrays in expressions
 - **Language Service** - IDE integration with completions, hover info, and highlighting
 
+## Playground Example
+
+Try out the expression evaluator and its language server capabilities directly in your browser at the [Playground](https://pro-fa.github.io/expr-eval/). The playground provides an interactive environment with:
+- Live expression evaluation
+- Code completions and IntelliSense
+- Syntax highlighting
+- Hover information for functions and variables
+
 ## Running Tests
 
 ```bash