Fix uglifyjs-webpack-plugin security vulnerability

[DimalChandrasiri]

Purpose

Resolve #300
Which causes the npm audit command to list a XSS vulnerability issue.

Goals

Fix XSS Vulnerability in plugin uglifyjs-webpack-plugin

Approach

Since the repository for uglifyjs-webpack-plugin is archived by the developer, the dependency list would not be fixed. Therefore according to a recommendation on StackOverflow will be removing the uglifyjs-webpack-plugin and will introduce a new minification plugin.

There is also a discussion which has happened in the webpack repository itself.