fix build for now

packages/extension-underline/src/index.ts

@@ -0,0 +1,42 @@
+import { Command, createMark } from '@tiptap/core'
+
+const Underline = createMark({
+  name: 'underline',
+
+  parseHTML() {
+    return [
+      {
+        tag: 'u',
+      },
+      {
+        style: 'text-decoration=underline',
+      },
+    ]
+  },
+
+  renderHTML({ attributes }) {
+    return ['u', attributes, 0]
+  },
+
+  addCommands() {
+    return {
+      underline: (): Command => ({ commands }) => {
+        return commands.toggleMark('underline')
+      },
+    }
+  },
+
+  addKeyboardShortcuts() {
+    return {
+      'Mod-u': () => this.editor.underline(),
+    }
+  },
+})
+
+export default Underline
+
+declare module '@tiptap/core/src/Editor' {
+  interface AllExtensions {
+    Underline: typeof Underline,
+  }
+}