Restore missing dependency `terser-webpack-plugin`

### Bug Report

Installing the CSS/JS assets fails due to missing dependency:
> [webpack-cli] Failed to load '/home/runner/work/admin/admin/webpack.config.js' config
> [webpack-cli] Error: Cannot find module 'terser-webpack-plugin'

|    Q        |   A
|------------ | ------
| Version(s)  | 7.x.x
