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/.eslintrc.js

@@ -0,0 +1,75 @@
+/**
+ * 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 fbjs = require('eslint-config-fbjs');
+
+// enforces copyright header and @format directive to be present in every file
+const pattern = /^\*\r?\n[\S\s]*Facebook[\S\s]* \* @format\r?\n/;
+
+const prettierConfig = {
+  requirePragma: true,
+  singleQuote: true,
+  trailingComma: 'all',
+  bracketSpacing: false,
+  jsxBracketSameLine: true,
+  parser: 'flow',
+};
+
+module.exports = {
+  parser: 'babel-eslint',
+  root: true,
+  extends: 'fbjs',
+  plugins: [...fbjs.plugins, 'header', 'prettier', '@typescript-eslint'],
+  rules: {
+    // disable rules from eslint-config-fbjs
+    'react/react-in-jsx-scope': 0, // not needed with our metro implementation
+    'no-new': 0, // new keyword needed e.g. new Notification
+    'no-catch-shadow': 0, // only relevant for IE8 and below
+    'no-bitwise': 0, // bitwise operations needed in some places
+    'consistent-return': 0,
+    'no-var': 2,
+    'prefer-const': [2, {destructuring: 'all'}],
+    'prefer-spread': 1,
+    'prefer-rest-params': 1,
+    'max-len': 0, // lets prettier take care of this
+    indent: 0, // lets prettier take care of this
+    'no-console': 0, // we're setting window.console in App.js
+    'no-multi-spaces': 2,
+    'prefer-promise-reject-errors': 1,
+    'no-throw-literal': 'error',
+    'no-extra-boolean-cast': 2,
+    'no-extra-semi': 2,
+    'no-unsafe-negation': 2,
+    'no-useless-computed-key': 2,
+    'no-useless-rename': 2,
+
+    // additional rules for this project
+    'header/header': [2, 'block', {pattern}],
+    'prettier/prettier': [2, prettierConfig],
+    'flowtype/object-type-delimiter': [0],
+  },
+  overrides: [
+    {
+      files: ['*.tsx', '*.ts'],
+      parser: '@typescript-eslint/parser',
+      rules: {
+        'prettier/prettier': [2, {...prettierConfig, parser: 'typescript'}],
+        '@typescript-eslint/no-unused-vars': [
+          1,
+          {
+            ignoreRestSiblings: true,
+            varsIgnorePattern: '^_',
+            argsIgnorePattern: '^_',
+            caughtErrorsIgnorePattern: '^_',
+          },
+        ],
+      },
+    },
+  ],
+};