WIP: Document usage examples

- [ ] Templates using child / custom elements
- [ ] Elaborate example for slots
- [x] Would like to set data via `fetch` / `Promises` inside the template. For example, ``. I should be able to set data variable in the script tag after promise is completed?
- [ ] Add example for integrating one of (vega-lite, d3 barchart) to element node using props.
- [ ] Explicitly mention using `e.target` in the example
- [ ] Document anti-patterns
- [x] Dynamic creation / custom element creation on the fly alternatives to
- [x] `$('elsewhere').html('')`
- [x] `document.createElement('main-element')` probably?
```html

<%= a %><%= b %>

$('body').on('click', 'child-element', console.log)

```
```javascript
$('elsewhere').html('')
```