Typescriptify the main process code (8/N)

Summary:
- Enabled typescript in "scripts" folder
- Converted start-dev-server.js to typescript

Reviewed By: passy

Differential Revision: D20066501

fbshipit-source-id: 23550cf3774e07fad0a8783831e3d574baee977f

types/ansi-to-html.d.ts

@@ -0,0 +1,14 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * 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 'ansi-to-html' {
+    export default class Filter {
+      toHtml: (input: string) => string;
+    }
+}