Documentation enhancements (#73)

docs/threepids/notification/sendgrid-handler.md

@@ -0,0 +1,7 @@
+# SendGrid Notification handler
+To be completed. See [raw possible configuration items](https://github.com/kamax-io/mxisd/blob/master/src/main/resources/application.yaml#L172).
+
+Enabled with:
+```yaml
+notification.handler.email: 'sendgrid'
+```