Update docs for Synapse: add anchor links to each other

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

docs/configuring-playbook-synapse.md

@@ -2,6 +2,8 @@
 
 By default, this playbook configures the [Synapse](https://github.com/element-hq/synapse) Matrix server, so that it works for the general case. If that's okay, you can skip this document.
 
+💡 See this page for details about maintaining Synapse: [Synapse maintenance](maintenance-synapse.md)
+
 ## Adjusting the playbook configuration
 
 ### Load balancing with workers

docs/maintenance-synapse.md

@@ -12,6 +12,8 @@ Table of contents:
 
 - [Make Synapse faster](#make-synapse-faster)
 
+💡 See this page for details about configuring Synapse: [Configuring Synapse](configuring-playbook-synapse.md)
+
 ## Purging old data with the Purge History API
 
 You can use the **[Purge History API](https://github.com/element-hq/synapse/blob/master/docs/admin_api/purge_history_api.md)** to delete old messages on a per-room basis. **This is destructive** (especially for non-federated rooms), because it means **people will no longer have access to history past a certain point**.