Add missing composer install step

Author: dkotter

.github/workflows/push-deploy.yml

@@ -22,6 +22,9 @@ jobs:
     - name: Build plugin
       run: npm run build
 
+    - name: Install Composer dependencies
+      run: composer install --no-dev
+
     - name: WordPress Plugin Deploy
       id: deploy
       uses: 10up/action-wordpress-plugin-deploy@stable