HTML inline style conversion

```html
<span style="color: red">I am red!</span>
```
generates
```nim
  span(style = "color: red"):
    text "I am red!"
```
but the correct is 
```nim
  span(style = style({color: "red".kstring})):
    text "I am red!"
```
The generated nim file must auto import the `karax/vstyles` if needed