Docs: Specify a manual npm install is needed

Author: mgol

README.md

@@ -9,6 +9,7 @@ Creating a release is as simple as cloning this repository and telling the scrip
 ```sh
 git clone git@github.com:jquery/jquery-release.git
 cd jquery-release
+npm install
 node release.js --remote=jquery/<project-name>
 ```