fix:add the type declaration of the "key" field (#1367)

* fix:add the type declaration of the "key" field

* change to a optional property and prettier code

src/components/GlobalFooter/index.d.ts

 import * as React from 'react';
 export interface IGlobalFooterProps {
   links?: Array<{
+    key?: string;
     title: React.ReactNode;
     href: string;
     blankTarget?: boolean;