Extract inline icons to SVG iconset (#1262)

bookmarks/templates/shared/modal_header.html

@@ -1,21 +1,12 @@
+{% load static %}
 <div class="modal-header">
   <h2 class="title">{{ title }}</h2>
   <button type="button"
           class="btn btn-noborder close"
           aria-label="Close dialog"
           data-close-modal>
-    <svg xmlns="http://www.w3.org/2000/svg"
-         width="24"
-         height="24"
-         viewBox="0 0 24 24"
-         stroke-width="2"
-         stroke="currentColor"
-         fill="none"
-         stroke-linecap="round"
-         stroke-linejoin="round">
-      <path stroke="none" d="M0 0h24v24H0z" fill="none"></path>
-      <path d="M18 6l-12 12"></path>
-      <path d="M6 6l12 12"></path>
+    <svg width="24" height="24">
+      <use href="{% static 'icons.svg' %}?v={{ app_version }}#close"></use>
     </svg>
   </button>
 </div>