returnsAPage
Whether a function returning this type can be an app's entry: a component's page (an element) or a main that
sets the page up itself (nothing, or a promise of nothing).
export const returnsAPage = (type: string): boolean => /^(void|undefined|Promise<void>|Promise<undefined>|(React\.)?(JSX\.)?Element|(React\.)?ReactNode|(React\.)?ReactElement(<.*>)?)$/.test( type, )