feat(v2): official CodeSandbox support (#3717)

* feat:added support for codesandbox

* added sandbox config file

* feat:added script to generate template for codesandbox

* added examples:generate script to package.json file

* added failing path to eslintignore

* added script to eslintignore

* added cleaning feature to script

* deleted sandbox script in root

* changed comment in codesandboxscript file

* update codesandboxscript.js + revert bad package.json changes

* eslint should check codesandboxscript

Co-authored-by: slorber <lorber.sebastien@gmail.com>

examples/facebook/sidebars.js

@@ -0,0 +1,15 @@
+/**
+ * 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
+ */
+
+module.exports = {
+  someSidebar: {
+    Docusaurus: ['doc1', 'doc2', 'doc3'],
+    Features: ['mdx'],
+  },
+};