Unit Test Fixes (#8245)

* Add @types/dompurify

* JS fix

* Update allowed tags

src/backend/InvenTree/InvenTree/settings.py

@@ -1277,6 +1277,7 @@ MARKDOWNIFY = {
             'li',
             'ol',
             'p',
+            'pre',
             's',
             'strong',
             'table',

src/backend/InvenTree/templates/js/translated/helpers.js

@@ -1,6 +1,7 @@
 {% load i18n %}
 
 /* globals
+    DOMPurify,
     EasyMDE,
     inventreeFormDataUpload,
     inventreeGet,