Lots of work making CodeMirror work. It is in a mostly useable state now.

package.json

@@ -87,9 +87,11 @@
   "type": "module",
   "dependencies": {
     "@codemirror/commands": "^6.8.1",
+    "@codemirror/gutter": "^0.19.9",
     "@codemirror/lang-css": "^6.3.1",
     "@codemirror/lang-html": "^6.4.9",
     "@codemirror/lang-javascript": "^6.2.3",
+    "@codemirror/lang-json": "^6.0.1",
     "@codemirror/lang-markdown": "^6.3.2",
     "@codemirror/language": "^6.11.0",
     "@codemirror/language-data": "^6.5.1",