customInput.js

import { api } from 'lwc'
import LightningInputRichText from 'lightning/inputRichText';

export default class CustomInput extends LightningInputRichText {
  @api
  getContent() {
    console.log('get content');
    return this.value;
  }

  @api
  setCustomContent(value) {
    console.log('set content');
    this.value = value;
  }

  constructor() {
    super();
  }
}