fix(theme): Move mask-icon outside show_meta_app_icon_tags guard

why: mask-icon (Safari pinned tab) should be independently configurable
     via theme_mask_icon option without requiring all app icon meta tags
     to be enabled (show_meta_app_icon_tags).
what:
- Remove mask-icon from inside show_meta_app_icon_tags conditional block
- Add standalone {%- if theme_mask_icon %} block at end of extrahead

Author: tony

packages/sphinx-gptheme/src/sphinx_gptheme/theme/page.html

@@ -67,12 +67,12 @@
   <meta name="apple-mobile-web-app-title" content="{{ theme_project_name }}">
 
   <link rel="apple-touch-icon" sizes="192x192" href="/_static/img/icons/icon-192x192.png">
-  {%- if theme_mask_icon %}
-  <link rel="mask-icon" href="{{ theme_mask_icon }}" color="grey">
-  {%- endif %}
 
   <!-- Microsoft -->
   <meta name="msapplication-TileColor" content="#ffffff">
   <meta name="msapplication-TileImage" content="/_static/img/icons/ms-icon-144x144.png">
   {% endif -%}
+  {%- if theme_mask_icon %}
+  <link rel="mask-icon" href="{{ theme_mask_icon }}" color="grey">
+  {%- endif %}
 {% endblock %}