Improve documentation for templates

[kaixin-hc]

Please confirm that you have searched existing issues in the repo

Yes, I have searched the existing issues

Any related issues?

#2459, #2385

What is the area that this feature belongs to?

Author Usability, Documentation

Is your feature request related to a problem? Please describe.

Users considering what template to use have no visual reference of the difference between templates. As we make this "quickstart" more fully featured, we should have working, meaningful demos - or at minimum some sort of visual reference for users to make a decision of what template suits them

Describe the solution you'd like

Minimal: on this page: https://markbind.org/userGuide/templates.html include modals/popups or tooltips with a screenshot of each template

More developed: Have a section with MarkBind demos that describe and use these templates and link that. One OSS project I think does this well, React-Admin has a great demos page: https://marmelab.com/react-admin/Demos.html which talks about the features in each demo, links a working demo, and also links the source code.

Describe alternatives you've considered

No response

Additional context

First raised in #2398 (comment)