Add link to Nextflow plugin docs (#15)

README.md

@@ -9,6 +9,8 @@ This project contains a simple Nextflow plugin called `nf-hello` which provides
 
 NOTE: If you want to use this project as a starting point for a custom plugin, you must rename the `plugins/nf-hello` folder and update `settings.gradle` with your plugin name.
 
+See the [Nextflow documentation](https://nextflow.io/docs/latest/plugins.html) for more information about developing plugins.
+
 ## Plugin structure
                     
 - `settings.gradle`