Dedupe customElements definitions

customElementDedupe.ts

export function customElementDedupe(): void {
  const define: Function = window.customElements.define.bind(window.customElements);
  window.customElements.define = (
    name: string,
    constructor: Function,
    options: object,
  ): void => {
    if (!window.customElements.get(name)) define(name, constructor, options);
  };
}