update README.md

README.md

 
 ## Usage
 
-Declare the package as a git dependency in `Packages/manifest.json`:
+Declare the package and its dependencies as git dependencies in `Packages/manifest.json`:
+    "com.unity.demoteam.attributes": "https://github.com/Unity-Technologies/com.unity.demoteam.attributes.git",
     ...
 }
 ```