added "configuring dendrite" entry

docs/configuring-playbook.md

@@ -47,6 +47,8 @@ When you're done with all the configuration you'd like to do, continue with [Ins
 
   - [Configuring Conduit](configuring-playbook-conduit.md), if you've switched to the [Conduit](https://conduit.rs) homeserver implementation (optional)
 
+  - [Configuring Dendrite](configuring-playbook-dendrite.md), if you've switched to the [Dendrite](https://matrix-org.github.io/dendrite) homeserver implementation (optional)
+
 - [Configuring Element](configuring-playbook-client-element.md) (optional)
 
 - [Storing Matrix media files on Amazon S3](configuring-playbook-s3.md) (optional)