I just found the amazing Stackblitz online VS Code editor. I created an Angular project and under dependencies installed the Bootstrap CSS framework but how
Add the following line of code in styles.css under src
@import url('https://unpkg.com/bootstrap@4.5.0/dist/css/bootstrap.min.css')
So to have the latest version of Bootstrap go to
https://getbootstrap.com/docs/4.5/getting-started/introduction/
Search for CSS CDN link, from that link copy the version (in my case 4.5.0) and replace it with the above import statement.