component.d.ts

declare global {
  // This is actually merging to the HTMLElement DOM Interface
  interface HTMLElement {
    componentOnReady?: () => Promise<this | null>;
  }

  interface HTMLStencilElement extends HTMLElement {
    componentOnReady(): Promise<this>;
    forceUpdate(): void;
  }
      
  namespace StencilComponents {
    interface Adder { }
  }

  interface HTMLAdderElement extends StencilComponents.Adder, HTMLStencilElement { }
}