minor #28332 Autoload symfony/contracts from the local repository (nicolas-grekas)

This PR was merged into the 4.2-dev branch.

Discussion
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Autoload symfony/contracts from the local repository

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

Required to have local changes on Contracts available while working on a PR.

Commits
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de6329a7d9 Autoload symfony/contracts from the local repository

composer.json

@@ -135,6 +135,12 @@
     "autoload-dev": {
         "files": [ "src/Symfony/Component/VarDumper/Resources/functions/dump.php" ]
     },
+    "repositories": [
+        {
+            "type": "path",
+            "url": "src/Symfony/Contracts"
+        }
+    ],
     "minimum-stability": "dev",
     "extra": {
         "branch-alias": {