chore(examples): add tree-shaking example (#24)

Add tree shaking example that corresponds with:

webpack/webpack.js.org#1508

Author: skipjack

examples/tree-shaking/package.json

@@ -0,0 +1,32 @@
+{
+  "name": "tree-shaking",
+  "version": "0.1.0",
+  "description": "Code examples for the tree-shaking guide.",
+  "main": "n/a",
+  "scripts": {
+    "build": "webpack",
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/TheDutchCoder/webpack-guides-code-examples.git"
+  },
+  "keywords": [
+    "tree",
+    "shaking",
+    "webpack",
+    "dead",
+    "code",
+    "removal"
+  ],
+  "author": "Greg Venech",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/TheDutchCoder/webpack-guides-code-examples/issues"
+  },
+  "homepage": "https://github.com/TheDutchCoder/webpack-guides-code-examples#readme",
+  "devDependencies": {
+    "uglifyjs-webpack-plugin": "^0.4.6",
+    "webpack": "^3.5.5"
+  }
+}

examples/tree-shaking/src/index.js

@@ -0,0 +1,14 @@
+import { cube } from './math.js';
+
+function component() {
+  var element = document.createElement('div');
+
+  element.innerHTML = [
+    'Hello webpack!',
+    '5 cubed is equal to ' + cube(5)
+  ].join('\n\n');
+
+  return element;
+}
+
+document.body.appendChild(component());

examples/tree-shaking/src/math.js

@@ -0,0 +1,7 @@
+export function square(x) {
+  return x * x;
+}
+
+export function cube(x) {
+  return x * x * x;
+}

examples/tree-shaking/webpack.config.js

@@ -0,0 +1,13 @@
+const path = require('path');
+const UglifyJSPlugin = require('uglifyjs-webpack-plugin');
+
+module.exports = {
+  entry: './src/index.js',
+  output: {
+    filename: 'bundle.js',
+    path: path.resolve(__dirname, 'dist')
+  },
+  plugins: [
+    new UglifyJSPlugin()
+  ]
+};