[4.x] Run async benchmark on CI to detect performance degredations

Author: WyriHaximus

.github/workflows/ci.yml

@@ -20,3 +20,17 @@ jobs:
           coverage: xdebug
       - run: composer install
       - run: vendor/bin/phpunit --coverage-text
+  benchmark-async:
+    name: "Benchmark: async (PHP ${{ matrix.php }})"
+    runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        php:
+          - 8.1
+    steps:
+      - uses: actions/checkout@v2
+      - uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+      - run: composer install
+      - run: time php examples/90-async-benchmark.php