While we do not have a feature for email templates or canned responses, we do have a workaround for this situation.
Create a work item called "Email Templates" or similar
Send emails with the canned responses you need to yourself
From your Triage, add these emails to the timeline for the work item you created
When you need a canned message, simply go to this work item and copy and paste these into your emails as required
When creating the work item, make sure you choose a start date and due date far into the future, so it doesn't pop into your work view or in your to-do list.