Upgrade CI action to use composer cache

.github/workflows/continuous-integration.yml

@@ -0,0 +1,36 @@
+name: Static analysis of live-broadcast-bundle
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  ci:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Validate composer.json and composer.lock
+        run: composer validate
+
+      - name: Cache Composer packages
+        id: composer-cache
+        uses: actions/cache@v2
+        with:
+          path: vendor
+          key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-php-
+
+      - name: Install dependencies
+        if: steps.composer-cache.outputs.cache-hit != 'true'
+        run: composer install --prefer-dist --no-progress --no-suggest
+
+      - name: Run PHPCS
+        run: ./vendor/bin/phpcs --standard=./vendor/escapestudios/symfony2-coding-standard/Symfony/ Broadcaster/ Command/ DependencyInjection/ Entity/ EventListener/ Exception/ Resources/ Service/ Tests/ LiveBroadcastBundle.php
+
+      - name: Run PHPUnit
+        run: ./vendor/bin/phpunit --coverage-text --colors