bug fixes

packages/ui-default/components/editor/mdeditor.ts

@@ -7,6 +7,7 @@ import MergeCells from 'markdown-it-merge-cells';
 import TOC from 'markdown-it-table-of-contents';
 import { config, MdEditor } from 'md-editor-rt';
 import Imsize from '../../backendlib/markdown-it-imsize';
+import katex from '../../backendlib/markdown-it-katex';
 import { Media } from '../../backendlib/markdown-it-media';
 import { xssProtector } from '../../backendlib/markdown-it-xss';
 
@@ -28,6 +29,7 @@ config({
     mdit.use(TOC);
     mdit.use(MergeCells);
     mdit.use(xssProtector);
+    mdit.use(katex);
     if (isProblemPage) {
       mdit.core.ruler.before('normalize', 'xss', (state) => {
         state.src = state.src.replace(/file:\/\//g, pagename === 'problem_create' ? `/file/${UserContext._id}/` : './file/');