Fix webpack's DllReferencePlugin.Options to allow manifest to be a string to support paths (#18902)

types/webpack/index.d.ts

@@ -783,7 +783,7 @@ declare namespace webpack {
             /**
              * An object containing `content` and `name`.
              */
-            manifest: { content: string, name: string };
+            manifest: { content: string, name: string } | string;
 
             /**
              * The name where the DLL is exposed.