clarify on the default and why you'd install this

Author: brian-mann

README.md

@@ -1,6 +1,14 @@
 # Cypress Browserify Preprocessor
 
-Cypress preprocessor for bundling JavaScript via browserify
+Cypress preprocessor for bundling JavaScript via browserify.
+
+This is the default preprocessor that comes packaged with Cypress. You'd typically need to install this if you want to modify the default options we've configured.
+
+Modifying the default options allows you to add support for things like: 
+
+- TypeScript
+- Babel Plugins
+- ES Presets
 
 ## Installation