add the docs for pixelfed link

Author: jessebot

README.md

@@ -22,3 +22,8 @@ helm show values pixelfed/pixelfed > values.yaml
 # install the chart
 helm install --namespace pixelfed --create-namespace pixelfed/pixelfed --values values.yaml
 ```
+
+## Notes
+
+You can find the general Pixelfed configuration docs here:
+https://docs.pixelfed.org/running-pixelfed/installation.html