Move desktop-related code to "desktop" subfolder (#872)

Summary:
Pull Request resolved: https://github.com/facebook/flipper/pull/872
Move all the JS code related to desktop app to "desktop" subfolder.

The structure of "desktop" folder:
- `src` - JS code of Flipper desktop app executing in Electron Renderer (Chrome) process. This folder also contains all the Flipper plugins in subfolder "src/plugins".
- `static` - JS code of Flipper desktop app bootstrapping executing in Electron Main (Node.js) process
- `pkg` - Flipper packaging lib and CLI tool
- `doctor` - Flipper diagnostics lib and CLI tool
- `scripts` - Build scripts for Flipper desktop app
- `headless` - Headless version of Flipper app
- `headless-tests` - Integration tests running agains Flipper headless version

Reviewed By: passy

Differential Revision: D20249304

fbshipit-source-id: 9a51c63b51b92b758a02fc8ebf7d3d116770efe9

desktop/types/JSONStream.d.tsx

@@ -0,0 +1,49 @@
+/**
+ * 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 'JSONStream' {
+  export interface Options {
+    recurse: boolean;
+  }
+
+  export function parse(pattern: any): NodeJS.ReadWriteStream;
+  export function parse(patterns: any[]): NodeJS.ReadWriteStream;
+
+  /**
+   * Create a writable stream.
+   * you may pass in custom open, close, and seperator strings. But, by default,
+   * JSONStream.stringify() will create an array,
+   * (with default options open='[\n', sep='\n,\n', close='\n]\n')
+   */
+  export function stringify(): NodeJS.ReadWriteStream;
+
+  /** If you call JSONStream.stringify(false) the elements will only be seperated by a newline. */
+  export function stringify(
+    newlineOnly: NewlineOnlyIndicator,
+  ): NodeJS.ReadWriteStream;
+  type NewlineOnlyIndicator = false;
+
+  /**
+   * Create a writable stream.
+   * you may pass in custom open, close, and seperator strings. But, by default,
+   * JSONStream.stringify() will create an array,
+   * (with default options open='[\n', sep='\n,\n', close='\n]\n')
+   */
+  export function stringify(
+    open: string,
+    sep: string,
+    close: string,
+  ): NodeJS.ReadWriteStream;
+  export function stringifyObject(): NodeJS.ReadWriteStream;
+  export function stringifyObject(
+    open: string,
+    sep: string,
+    close: string,
+  ): NodeJS.ReadWriteStream;
+}