qa: add benchmark workflow

Now that the master branch has the benchmark mechanism we can introduce
a workflow that compares the PR code performance against the targeted
branch.

.github/workflows/benchmark.yml

@@ -0,0 +1,36 @@
+name: Benchmark
+on: [pull_request]
+jobs:
+  benchmark:
+    name: Benchmark
+    runs-on: ubuntu-latest
+    env:
+      php-version: '8.3'
+    steps:
+      - name: Checkout target branch
+        uses: actions/checkout@v3
+        with:
+          ref: ${{ github.base_ref }}
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ env.php-version }}
+          extensions: ${{ env.php-extensions }}
+          ini-values: zend.assertions=1
+          coverage: none # Xdebug is installed by default, so we remove it manually
+
+      - uses: "ramsey/composer-install@v2"
+
+      - name: Creating a baseline benchmark from target branch
+        run: composer run-script benchmark-baseline
+
+      - name: Checkout PR code
+        uses: actions/checkout@v3
+        with:
+          clean: false
+
+      - uses: "ramsey/composer-install@v2"
+
+      - name: Compare the performances against the baseline
+        run: composer run-script benchmark-compare