How to import a template file with HTML markup to use for sending email notifications? I want to send the email notifications to users of the site. I have a basic template file with the HTML markup I want to send in the email.

How do I import that HTML file (which is in the root folder of the project) in my module?
If the module doesn't allow importing it, just copy the markup and put it in your relevant Email template, inside your module.

Otherwise, add such importing option by customizing to module, or try another.