[chore, doc] Split out the "vendor"/3rd party code to its own bundle

Included 'vendor.bundle.js' as it is referenced. So this will give a
baseline to compare against future builds. But ideally this will only
change when updating dependency versions.

CONTRIBUTING.md

@@ -88,7 +88,8 @@ the following rules:
    the changes to the UI
  - If your changes affect Netscript, provide some 
    scripts that can be used to test the Netscript changes. 
- - Do not check in the bundled engine (dist\engine.bundle.js)
+ - Do not check in any bundled files (`dist\*.bundle.js`). These will be
+   updated as part of official releases.
 
 ## As a Documentor
 To contribute to BitBurner documentation, you will need to have Python

index.html

@@ -950,6 +950,7 @@
         <div class="loaderspinner"></div>
         <div class="loaderlabel">Loading Bitburner...</div>
     </div>
+    <script src="dist/vendor.bundle.js"></script>
     <script src="dist/engine.bundle.js"></script>
 </body>
 </html>

webpack.config.js

@@ -48,7 +48,16 @@ module.exports = (env, argv) => ({
         namedModules: false,
         namedChunks: false,
         minimize: argv.mode !== 'development',
-        portableRecords: true
+        portableRecords: true,
+        splitChunks: {
+            cacheGroups: {
+                vendor: {
+                    test: /[\\/]node_modules[\\/]/,
+                    name: 'dist/vendor',
+                    chunks: 'all'
+                }
+            }
+        }
     },
     devServer: {
         publicPath: "/dist",