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/scripts/prepare-watchman-config.js

@@ -0,0 +1,31 @@
+/**
+ * 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
+ */
+
+const path = require('path');
+const util = require('util');
+const {exists: existsImport, copyFile} = require('fs');
+const exists = util.promisify(existsImport);
+
+const desktopRootDir = path.resolve(__dirname, '..');
+const rootDir = path.resolve(desktopRootDir, '..');
+const hasGit = exists(path.join(rootDir, '.git'));
+
+async function prepareWatchmanConfig(dir) {
+  const hasWatchmanConfig = exists(path.join(dir, '.watchmanconfig'));
+  if ((await hasGit) && !(await hasWatchmanConfig)) {
+    console.log(`Creating .watchmanconfig in ${dir}`);
+    await util.promisify(copyFile)(
+      path.join(dir, '_watchmanconfig'),
+      path.join(dir, '.watchmanconfig'),
+    );
+  }
+}
+
+prepareWatchmanConfig(rootDir);
+prepareWatchmanConfig(path.join(desktopRootDir, 'static'));