Improve styling for mixed list styles

Tasks in an ordered list will now also show their numbers.

Closes #2488

Related to #3921

app/assets/stylesheets/framework/lists.scss

@@ -88,8 +88,14 @@ ul.bordered-list {
   }
 }
 
-li.task-list-item {
+ul.task-list {
+  li.task-list-item {
     list-style-type: none;
+  }
+
+  ul:not(.task-list) {
+    padding-left: 1.3em;
+  }
 }
 
 ul.content-list {

app/assets/stylesheets/pages/notes.scss

@@ -109,13 +109,9 @@ ul.notes {
           }
         }
 
-        // Reduce left padding of first task list ul element
-        ul.task-list:first-child {
-          padding-left: 10px;
-
-          // sub-tasks should be padded normally
-          ul {
-            padding-left: 20px;
+        ul.task-list {
+          ul:not(.task-list) {
+            padding-left: 1.3em;
           }
         }