Alias paths in tsconfig.json and webpack not working

[robinyo]

See: https://robferguson.org/blog/2017/11/22/working-with-typescript-webpack-and-ionic-3/

Resources:

• GitHub: Easy to use environment variables for Ionic 3
• GitHub: Ionic CLI - Issue 1205 - Environment variable configuration
• TypeScript docs: tsconfig.json
  
• webpack docs: webpack.config.js