pub fn build(self) -> Capsule<G, P> {
        Capsule {
            inner: Entity::from(self.template_inner),
            capsule_view: self.capsule_view,
            fallback: self.fallback,
        }
    }
Builds a full [`Capsule`] from this [`CapsuleInner`], consuming it in
the process. Once called, the capsule cannot be modified anymore,
and it will be placed into a smart pointer, allowing it to be cloned
freely with minimal costs.

You should call this just before you return your capsule.
packages/perseus/src/template/capsule.rs