Add support for custom HTML files based on templates

When creating a custom template, I couldn't find a way to generate custom HTML files based on the project template (for instance, create an additional page that lists all functions or any other useful page).

Please add an option to add additional files based on templates (for example, adding a configuration in config.json that would allow to generate `MyFile.html` that is based on `MyFile.mtt`

Thank you very much!

P.S. if such thing is possible, I would be grateful if that would be added to the documentation, as I was unable to find anything.