N°2651 rollback gitignore for lib tests dirs

Too dangerous ! We'll work properly on this but for 2.8

lib/symfony/framework-bundle/Tests/DependencyInjection/Fixtures/yml/assets.yml

@@ -0,0 +1,21 @@
+framework:
+    assets:
+        version: SomeVersionScheme
+        version_format: '%%s?version=%%s'
+        base_urls: http://cdn.example.com
+        packages:
+            images_path:
+                base_path: '/foo'
+            images:
+                version: 1.0.0
+                base_urls: ["http://images1.example.com", "http://images2.example.com"]
+            foo:
+                version: 1.0.0
+                version_format: '%%s-%%s'
+            bar:
+                base_urls: ["https://bar2.example.com"]
+            bar_version_strategy:
+                base_urls: ["https://bar_version_strategy.example.com"]
+                version_strategy: assets.custom_version_strategy
+            json_manifest_strategy:
+                json_manifest_path: '/path/to/manifest.json'