centered container

pages/_layouts/default.html

@@ -9,7 +9,7 @@ layout: base
 	{% include layout/navbar-secondary.html %}
 
 	<div class="content">
-		<div class="container">
+		<div class="container{% if page.container-centered %} d-flex flex-column justify-content-center{% endif %}">
 			{% if page-header %}
 				{% include layout/page-header.html title=page-header description=page.page-header-description actions=page.page-header-actions pretitle=page.page-header-pretitle %}
 			{% endif %}

pages/blank.html

@@ -3,6 +3,7 @@ title: Blank page
 blank: true
 done: true
 menu: base.blank
+container-centered: true
 ---
 
 {% include ui/empty.html button-text="Add your first client" button-icon="plus" illustration=true illustration-src="undraw_printing_invoices_5r4r.svg" %}