message: README: update plugin instructions to not always run yarn
diff: @@ -58,10 +58,10 @@ The final `yarn start` command should open a local instance of Backstage in your
  ### Creating a Plugin
  -To create a new plugin, run the following:
  +To create a new plugin, make sure you're run `yarn` to install dependencies, then run the following:
  ```bash
  -$ yarn && yarn create-plugin
  +$ yarn create-plugin
  ```
  This will prompt you to enter an ID for your plugin, and then create your plugin inside the `packages/plugins/` directory. The plugin will be automatically included in the app by modifing the app's `package.json` and `src/plugins.ts`.
  