Non-string replacement value

Hi, is there a technical reason why the replacement value must be a string? My use-case is that I load in an object and then use that to replace values in a CSS file, but some values should be numbers.

For example, this fails:

```css
padding: {{ padding }};
```

```js
data = {
  padding: 0, // this fails, but works as a string: "0"
}
```