docs: Example for range/each

## Synopsis

There are no examples for range/each.

```handlebars
{{range $e := .providers}}
<li><a href="/login/w/{{$e}}" class="button">
  <i class="fa fa-{{$e}}"></i> {{ucfirst $e}}
</a></li>
{{end}}
```

https://golang.org/pkg/text/template/