Update FormData methods with appropriate types

Author: NColey

src/lib/dom.iterable.d.ts

@@ -8,17 +8,17 @@ interface FormData {
     /**
      * Returns an array of key, value pairs for every entry in the list
      */
-    entries(): IterableIterator<[string, any]>;
+    entries(): IterableIterator<[string, string | File]>;
     /**
      * Returns a list of keys in the list
      */
     keys(): IterableIterator<string>;
     /**
      * Returns a list of values in the list
      */
-    values(): IterableIterator<any>;
+    values(): IterableIterator<string | File>;
 
-    [Symbol.iterator](): IterableIterator<any>;
+    [Symbol.iterator](): IterableIterator<string | File>;
 }
 
 interface NodeList {