add folding to editor

Author: xiaoxinghu

packages/editor/lib/setup.js

@@ -1,10 +1,16 @@
-import { EditorView, highlightActiveLine, showPanel } from '@codemirror/view'
+import { foldGutter, toggleFold } from '@codemirror/language'
+import {
+  EditorView,
+  highlightActiveLine,
+  keymap,
+  showPanel,
+} from '@codemirror/view'
 import { org } from '@orgajs/cm-lang'
-import theme from './theme.js'
 import { cleanupPlugin } from './plugins/cleanup.js'
+import theme from './theme.js'
 
 /**
- * @returns {import('@codemirror/view').Panel')}
+ * @returns {import('@codemirror/view').Panel}
  */
 function footer() {
   const dom = document.createElement('div')
@@ -17,11 +23,20 @@ function footer() {
   }
 }
 
+const keys = [
+  {
+    key: 'Tab',
+    run: toggleFold,
+  },
+]
+
 export const setup = (() => [
   highlightActiveLine(),
+  foldGutter(),
   org(),
   theme,
   EditorView.lineWrapping,
   cleanupPlugin,
   showPanel.of(footer),
+  keymap.of(keys),
 ])()