Set license to MIT

Summary:
The entire repo is MIT (unless stated otherwise) but
without the flag, yarn is very noisy on every startup.

{F668266100}

Reviewed By: timur-valiev

Differential Revision: D31429016

fbshipit-source-id: 11a963181dc309a251e6c71a9a16ab93d12b7f93

website/package.json

@@ -32,5 +32,6 @@
     "ws": "8.2.0",
     "trim": "1.0.1",
     "immer": "^9.0.6"
-  }
+  },
+  "license": "MIT"
 }