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/headless-tests/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "headless-tests",
+  "version": "1.0.0",
+  "main": "index.js",
+  "scripts": {
+    "test": "jest",
+    "test:debug": "node --inspect node_modules/.bin/jest --runInBand"
+  },
+  "jest": {
+    "transform": {
+      "^.+\\.jsx?$": "babel-jest"
+    }
+  },
+  "devDependencies": {
+    "jest": "^24.7.1"
+  },
+  "license": "MIT",
+  "dependencies": {
+    "@babel/preset-env": "^7.8.3",
+    "@babel/preset-flow": "^7.8.3",
+    "babel-jest": "^24.8.0",
+    "canonical-json": "^0.0.4",
+    "lodash.memoize": "^4.1.2"
+  }
+}