CodeMirror V6でline numberを使いたい場合は

version

    "@codemirror/commands": "^6.2.4",
    "@codemirror/lang-json": "^6.0.1",
    "@codemirror/state": "^6.2.1",
    "@codemirror/view": "^6.16.0",
    "codemirror": "^6.0.1",

コード

import { EditorState, Compartment } from "@codemirror/state";
import { EditorView, lineNumbers } from "@codemirror/view"; // lineNumbersをインポート

declare var editor;

editor = new EditorView({
  state: EditorState.create({
    doc: `{}`,
    extensions: [
      new Compartment().of(lineNumbers()), // Compartmentする
    ],
  }),
  parent: document.querySelector("#id"),
});