Experiment: Templates

**Describe the solution you'd like**
I'd like to add an optional `protected readonly template` property to a component so that the render function could auto-apply it automatically (replacing the need for a `render` function). This would require a template engine to be used.

Check `templates` branch for a working example.

Review the templates branch for the working example, then trace how the component's render function is currently used. Determine the scope of an optional protected readonly template property and the required template engine; done should allow the template to be applied automatically without a render function.

Written by the indexing model from the issue text.