Load scripts in the head AND bottom of the page?
You have to add additional libraries: https://ffwagency.com/blog/managing-css-and-javascript-files-drupal-8-libraries

So in my theme.info.yaml 

libraries:
  - THEME-NAME/global
  - THEME-NAME/custom


In my theme.libraries.yaml file:

global:
  version: 1.x
  css:
    base:
      /ui/style.css: {preprocess: false, minified: false}
  js:
    /ui/application.js: {preprocess: false, minified: false, weight: '-99'}

custom:
  version: 1.x
  header: true
  js:
    /ui/head.js: {}