Custom element namespace example

## Example Request

There is some documentation about how the html namespace works in the [html crate](https://docs.rs/dioxus-html/0.6/dioxus_html/index.html#overview), but we don't have any full example that shows how to create a custom element in the examples folder

We do have an example that shows how to create web components that follow the dash naming convention [here](https://github.com/DioxusLabs/dioxus/blob/main/examples/web_component.rs), but not all web components do