Webpack only runs on port 8080

[EvanBurbidge]

This PR contains:

A fix for issue https://github.com/salomonelli/best-resume-ever/issues/291 where the user has requested that Webpack runs on other ports if 8080 is in use. I've introduced the npm package detect-port which then allows the program to search for the next available port.

Describe the problem you have without this PR

https://github.com/salomonelli/best-resume-ever/issues/291