feat: katex in markdown preview + xss fix for svg

server/modules/rendering/html-security/renderer.js

@@ -29,10 +29,10 @@ module.exports = {
           path: ['d', 'style'],
           pre: ['class', 'style'],
           section: ['class', 'style'],
-          span: ['class', 'style'],
+          span: ['class', 'style', 'aria-hidden'],
           strong: ['class', 'style'],
           summary: ['class', 'style'],
-          svg: ['width', 'height', 'viewBox', 'preserveAspectRatio', 'style'],
+          svg: ['width', 'height', 'viewbox', 'preserveaspectratio', 'style'],
           table: ['border', 'class', 'id', 'style', 'width'],
           tbody: ['class', 'style'],
           td: ['align', 'class', 'colspan', 'rowspan', 'style', 'valign'],