Extend nested_list example with examples of runtime-generated list using html_nested!

[Mingun]

This is about:

• A typo
• Innaccurate/misleading documentation (e.g. technically incorrect advice)
• Undocumented code
• Outdated documentation
• Other

Problem
Currently nested_list example shows only how to create components with restricted children type for static lists. But in many use cases list would contain dynamic data. So it is good to include example of using html_nested! macro.

See #1530 (comment)

Questionaire (Optional)

• I'd like to write this documentation
• I'd like to write this documentation but I'm not sure what's needed
• I don't have time to add this right now, but maybe later