Add information about mxisd email template customization

Related to #108 (Github Pull Request).

CHANGELOG.md

@@ -1,3 +1,11 @@
+# 2019-03-07
+
+## Ability to customize mxisd's email templates
+
+Thanks to [Sylvia van Os](https://github.com/TheLastProject), mxisd's email templates can now be customized easily.
+To learn more, see the [Customizing email templates](docs/configuring-playbook-mxisd.md#customizing-email-templates) documentation page.
+
+
 # 2019-03-05
 
 ## Discord bridging support

docs/configuring-playbook-mxisd.md

@@ -18,6 +18,12 @@ matrix_mxisd_matrixorg_forwarding_enabled: true
 ```
 
 
+## Customizing email templates
+
+If you'd like to change the default email templates used by mxisd, take a look at the `matrix_mxisd_threepid_medium_email_custom_` variables
+(in the `roles/matrix-mxisd/defaults/main.yml` file.
+
+
 ## Additional features
 
 What this playbook configures for your is some bare minimum Identity Server functionality, so that you won't need to rely on external 3rd party services.