title: bundle size: Is it possible to set lit-element as a peer dependency?
body: <p>I noticed there is much code added to the bundled js for a simple lit-element based web component, and react components set react as a peer dependency so only one react runtime is bundled, since web components are framework-agnostic, if i used lit-element in my project and i'm using another external WC built with lit-element, will lit-element be bundled twice?</p>