placeholder function

I am using codemirror 6.0 I would like to add placeholder function, can you teach me? The documentation says to introduce an extension, how to introduce this extension, please give me a sample, thank you Waiting online!

Something like this -

import { basicSetup } from 'codemirror';
import { EditorView, placeholder } from "@codemirror/view";
import { EditorState } from "@codemirror/state";

let startState = EditorState.create({
  extensions: [
    placeholder("Write your placeholder text here"),

   let view = new EditorView({
      state: startState,
      parent: yourRefHere,
      plugin: []