add some packages

node_modules/babel-plugin-transform-remove-undefined/README.md

@@ -0,0 +1,63 @@
+# babel-plugin-transform-remove-undefined
+
+For variable assignments, this removes rvals that evaluate to `undefined`
+(`var`s in functions only).
+For functions, this removes return arguments that evaluate to `undefined`.
+
+## Example
+
+**In**
+
+```javascript
+let a = void 0;
+function foo() {
+  var b = undefined;
+  return undefined;
+}
+```
+
+**Out**
+
+```javascript
+let a;
+function foo() {
+  var b;
+  return;
+}
+```
+
+## Installation
+
+```sh
+npm install babel-plugin-transform-remove-undefined
+```
+
+## Usage
+
+### Via `.babelrc` (Recommended)
+
+**.babelrc**
+
+```json
+{
+  "plugins": ["babel-plugin-transform-remove-undefined"]
+}
+```
+
+### Via CLI
+
+```sh
+babel --plugins babel-plugin-transform-remove-undefined script.js
+```
+
+### Via Node API
+
+```javascript
+require("@babel/core").transform("code", {
+  plugins: ["babel-plugin-transform-remove-undefined"]
+});
+```
+
+## Options
+
++ `tdz` - Detect usages before declaration/initialization in let/const(throws) and var(void 0)