feature(input): ref focus属性报错

[zhoulujun]

TS2339: Property 'focus' does not exist on type '{ $: ComponentInternalInstance; $data: {}; $props: Partial{ type: string; behavior: "simplicity" | "normal"; disabled: boolean; step: number; placeholder: string; ... 15 more ...; withValidate: boolean; }> & Omit...>; ... 10 more ...; $watch(source: string | Function, cb: Function, options?: WatchOptions...>): Wa...'.