docs(docs): update nx plugin submission guide

docs/shared/nx-plugin.md

@@ -255,6 +255,7 @@ After that, you can then install your plugin like any other npm package,
 
 Nx provides a utility (`nx list`) that lists all approved plugins. To submit your plugin, please follow the steps below:
 
+- Fork the [Nx repo](https://github.com/nrwl/nx/fork) (if you haven't already)
 - Update the [`community/approved-plugins.json` file](https://github.com/nrwl/nx/blob/master/community/approved-plugins.json) with a new entry for your plugin that includes name, url and description
 - Use the following commit message template: `chore(core): nx plugin submission [PLUGIN_NAME]`
 - push your changes, and run `yarn submit-plugin`