docs: update

Author: Guillaume Chau

docs/plugin-dev-ui.md

@@ -331,6 +331,8 @@ A Client addon is a JS bundle which is dynamically loaded into the cli-ui. It is
 
 The recommended way to create a Client addon is by creating a new project using vue-cli 3. You can either do this in a subfolder of your plugin or in a different npm package.
 
+Install `@vue/cli-ui` as a dev dependency.
+
 Then add a `vue.config.js` file with the following content:
 
 ```js