docs(@ngtools/webpack): added warning, an example and a table of differences when building with prod flag

Author: Stian Standahl

docs/documentation/build.md

@@ -64,6 +64,30 @@ ng build --bh /myUrl/
 All builds make use of bundling, and using the `--prod` flag in  `ng build --prod`
 or `ng serve --prod` will also make use of uglifying and tree-shaking functionality.
 
+**Note:** It is not recommended using `[class].constructor.name` while using the
+`--prod` build flag. Since the name of the class will be uglified.
+#### Example
+```js
+// Outputing router events to log
+router.events.map(event => console.log(event.constructor.name));
+
+// Output without --prod flag:
+// NavigationStart
+// RoutesRecognized
+// NavigationEnd
+
+// With --prod flag:
+// t
+// v
+// c
+```
+
+#### Difference between building with or without `---prod` flag
+|              | With | Without |
+|--------------|:----:|:-------:|
+| Tree-shaking |  x   |    x    |
+| Uglifying    |  x   |         |
+
 ## Options
 `--watch` (`-w`) rebuild when files change