Function mount 

pub fn mount<S, V>(
    prefix: impl Into<String>,
    children: Vec<ErasedComponent<S, V>>,
    merge: impl Fn(Vec<V>) -> V + Send + Sync + 'static,
) -> ErasedComponent<S, V>
where
    S: Send + Sync + 'static,
    V: 'static,

Mount several components as one. Views merge left-to-right with merge; transitions are concatenated then namespaced under prefix.