Function sauron::jss::class_namespaced

pub fn class_namespaced<MSG>(
    namespace: impl ToString, 
    class_names: impl ToString
) -> Attribute<&'static str, &'static str, AttributeValue, Event, MSG>

return a class attribute where the classnames are transformed with namespace example:

use sauron_core::jss::class_namespaced;
use sauron_core::Attribute;
use sauron_core::html::attributes::class;

let expected: Attribute<()> = class("frame__border".to_string());
assert_eq!(expected, class_namespaced("frame", "border"));

let expected: Attribute<()> =
    class("frame__border frame__corner".to_string());
assert_eq!(expected, class_namespaced("frame", "border corner"));