Looks like the way you have your Angular config setup in your example, you need to put style imports in the ./src/styles.css
file to have them imported correctly.
// In ./src/app/app.component.ts
import { Component, OnInit } from '@angular/core';
// remove this line
// import 'grapesjs/dist/css/grapes.min.css';
import grapesjs from 'grapesjs';
// In ./src/styles.css
// add the style import here
@import 'grapesjs/dist/css/grapes.min.css';
At this stage it still looks a bit bare. If you want it to look like the grapesjs web demo, that uses the grapesjs-webpage-preset
plugin, so you might want to install and import that too.
Here's an example stackblitz with the above changes: https://stackblitz.com/edit/angular-ivy-bf8xe8