gzip Angular files after build

npm i gzipper -g

or locally to devDependencies

npm i gzipper -D

use gzipper with your build commands (e.g. Angular CLI)

"scripts": {
    "build": "ng build && gzipper --verbose ./dist"
  }

compress files to a certain directory ./gzipped

"scripts": {
    "build": "ng build && gzipper --verbose ./dist ./gzipped"
  }

build.bat

ng build --prod --aot && gzipper --verbose ./dist

References
https://www.npmjs.com/package/gzipper