Add function, which is inverse function of STSHtmlEncode

sharepoint/SharePoint.d.ts

@@ -182,6 +182,7 @@ declare class _spPageContextInfo {
 }
 
 declare function STSHtmlEncode(value: string): string;
+declare function STSHtmlDecode(value: string): string;
 
 declare function AddEvtHandler(element: HTMLElement, event: string, func: EventListener): void;