[Backport to 4.0] - Configure project to download and integrate jstimezonedetect library automatically

CMS-6954 uses the jstimezonedetect library. Currently, its minified version jstz.min.js is copied directly to the CMS project. It means that CMS contains external library code.

This setup can be improved by configure jstimezonedetect as a npm dependency, then jstz.min.js file will be copied to proper location during compilation.