Support hard breaks in content editor

app/assets/javascripts/content_editor/services/create_editor.js

@@ -12,6 +12,7 @@ import {
   BulletList,
   OrderedList,
   ListItem,
+  HardBreak,
 } from 'tiptap-extensions';
 import { PROVIDE_SERIALIZER_OR_RENDERER_ERROR } from '../constants';
 import CodeBlockHighlight from '../extensions/code_block_highlight';
@@ -36,6 +37,7 @@ const createEditor = async ({ content, renderMarkdown, serializer: customSeriali
       new ListItem(),
       new OrderedList(),
       new CodeBlockHighlight(),
+      new HardBreak(),
     ],
     editorProps: {
       attributes: {

spec/frontend/fixtures/api_markdown.yml

@@ -48,3 +48,7 @@
     3. list item 3
 - name: image
   markdown: '![alt text](https://gitlab.com/logo.png)'
+- name: hard_break
+  markdown: |-
+    This is a line after a\
+    hard break