Add composer validation as separate action

Author: vpodorozh

.github/workflows/test_extension.yml

@@ -10,7 +10,7 @@ permissions:
   contents: read
 
 jobs:
-  build:
+  validate-composer:
 
     runs-on: ubuntu-latest
 
@@ -20,6 +20,15 @@ jobs:
       - name: Validate composer.json and composer.lock
         run: composer validate
 
+  build:
+
+    runs-on: ubuntu-latest
+
+    needs: validate-composer
+
+    steps:
+      - uses: actions/checkout@v3
+
       - name: Cache Composer packages
         id: composer-cache
         uses: actions/cache@v3