Convert Flipper plugin "mobileboost" to TypeScript

Summary: Bugfix for Tab.tsx + implicitly typed react vizualized

Reviewed By: danielbuechele

Differential Revision: D17205342

fbshipit-source-id: 48d29c583f0790af46f3d9c8d0280015b58d56aa

src/ui/components/Tab.tsx

@@ -38,6 +38,6 @@ export type Props = {
   width?: WidthProperty<number>;
 };
 
-export default function Tab(_props: Props) {
+export default function Tab(_props: Props): JSX.Element {
   throw new Error("don't render me");
 }

types/react-virtualized.d.tsx

@@ -0,0 +1,11 @@
+/**
+ * Copyright 2018-present Facebook.
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ * @format
+ */
+
+declare module 'react-virtualized' {
+  const AutoSizer: any;
+  const Collection: any;
+}