minor #11623 add symfony/yaml suggestion to composer.json (xabbuh)

This PR was merged into the 2.5 branch.

Discussion
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add symfony/yaml suggestion to composer.json

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Commits
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dcce035 add symfony/yaml suggestion to composer.json

src/Symfony/Bundle/FrameworkBundle/composer.json

@@ -43,6 +43,7 @@
         "symfony/finder": "For using the translation loader and cache warmer",
         "symfony/form": "For using forms",
         "symfony/validator": "For using validation",
+        "symfony/yaml": "For using the config:debug and yaml:lint commands",
         "doctrine/cache": "For using alternative cache drivers"
     },
     "autoload": {