Add bootstrap 4 to angular 6 project

1. Do in terminal:
	npm install --save bootstrap

2. Add to styles.css:
	@import "~bootstrap/dist/css/bootstrap.css"

3.Add to index.html:
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
  <script src="https://npmcdn.com/[email protected]/dist/js/tether.min.js"></script>