Enable faster development loop

The current development workflow with spago bundle-app adds a 15-second delay (on my system) between making changes and seeing the results in your browser.

There are other strategies to achieve near-instant page refreshes with saved changes, such as with webpack in #187 and #192.

Start by examining the current spago bundle-app workflow and the webpack approaches discussed in issues #187 and #192. Determine how the development loop can provide near-instant browser refreshes after saved changes, and verify that the resulting workflow removes the reported delay.