Properly support window.printJS and module print

Expose `printJS` function on the window object (if window exists) (see `/src/index.js`)

Build package via Webpack as a UMD library and purposefully rename
`print` to avoid conflicts.
Update Typescript typings file to reflect this.

Good resources:
http://siawyoung.com/coding/javascript/exporting-es6-modules-as-single-scripts-with-webpack.html
https://webpack.js.org/guides/author-libraries/
https://stackoverflow.com/questions/40294870/module-exports-vs-export-default-in-node-js-and-es6/40295288#40295288

README.md

@@ -26,7 +26,7 @@ yarn add print-js
 When installing via npm or yarn, import the library into your project:
 
 ```
-import printJS from 'print-js'
+import print from 'print-js'
 ```
 
 ## Documentation

index.d.ts

@@ -1,5 +1,3 @@
-import 'print-js/dist/print';
-
 declare type PrintTypes = 'pdf' | 'html' | 'image' | 'json';
 
 export interface Configuration {
@@ -32,6 +30,6 @@ export interface Configuration {
   scanStyles?: boolean;
 }
 
-declare var printJS: (params: string | Configuration) => void;
+declare var print: (params: string | Configuration) => void;
 
-export default printJS;
+export default print;

src/index.js

@@ -7,4 +7,4 @@ if (typeof window !== 'undefined') {
   window.printJS = printJS
 }
 
-module.exports = printJS
+export default printJS

webpack.config.js

@@ -8,7 +8,7 @@ module.exports = {
     './src/index.js'
   ],
   output: {
-    library: 'printJS',
+    library: 'print',
     libraryTarget: 'umd',
     path: path.resolve(__dirname, 'dist'),
     filename: 'print.js',