Document automatic cleanup of unused assets in README.md

README.md

@@ -74,6 +74,26 @@ into the form found in the backend module and store it along with your Neos user
 When everything works out fine, Neos will report that the connection was successful (and if not, you'll see an error
 message with further details).
 
+## Cleaning up unused assets
+
+Whenever a pixx.io asset is used in Neos, the media file will be copied automatically to the internal Neos asset
+storage. As long as this media is used somewhere on the website, Neos will flag this asset as being in use. 
+When an asset is not used anymore, the binary data and the corresponding metadata can be removed from the internal
+storage. While this does not happen automatically, it can be easily automated by a recurring task, such as a cron-job.
+
+In order to clean up unused assets, simply run the following command as often as you like:
+
+```bash
+./flow media:removeunused --asset-source flownative-pixxio
+``` 
+
+If you'd rather like to invoke this command through a cron-job, you can add two additional flags which make this
+command non-interactive:
+
+```bash
+./flow media:removeunused --quiet --assume-yes --asset-source flownative-pixxio
+``` 
+
 ## Credits and license
 
 This plugin was sponsored by [pixx.io](https://www.pixxio-bildverwaltung.de/) and its initial version was developed by