Fix save) triggers 'not allowed to be changed'

"500 PUT options. Option 'allowedHtmlTags' is not allowed to be changed"

Note: the "allowed to change" list is set on startup. When a new option
is added Trilium must be restarted.

src/routes/api/options.ts

@@ -66,7 +66,8 @@ const ALLOWED_OPTIONS = new Set([
     'editedNotesOpenInRibbon',
     'locale',
     'firstDayOfWeek',
-    'textNoteEditorType'
+    'textNoteEditorType',
+    'allowedHtmlTags', // Allow configuring HTML import tags
 ]);
 
 function getOptions() {