Add UMD build

Author: abraham

package.json

@@ -2,11 +2,11 @@
   "name": "@abraham/reflection",
   "version": "0.3.0",
   "description": "Lightweight ES Module implementation of reflect-metadata",
-  "main": "dist/index.js",
+  "main": "dist/index.umd.js",
   "module": "dist/index.js",
   "types": "dist/index.d.ts",
   "scripts": {
-    "build": "tsc",
+    "build": "tsc && rollup -c",
     "clean": "rimraf dist",
     "prebuild": "npm run clean",
     "prepare": "npm run build",
@@ -38,6 +38,7 @@
     "jest": "23.4.1",
     "pkg-ok": "2.2.0",
     "rimraf": "2.6.2",
+    "rollup": "0.63.4",
     "ts-jest": "23.0.1",
     "typescript": "2.9.2"
   },

rollup.config.js

@@ -0,0 +1,8 @@
+export default {
+  input: 'dist/index.js',
+  output: {
+    file: 'dist/index.umd.js',
+    format: 'umd',
+    name: '@abraham/reflection',
+  }
+};