Resize screenshots

templates/front/welcome.html

@@ -143,7 +143,9 @@
     <div class="col-sm-8">
         <img
             class="img-responsive"
-            src="{% static 'img/my_checks.png' %}" alt="My Checks page" />
+            src="{% static 'img/my_checks.png' %}"
+            srcset="{% static 'img/my_checks.png'%} 1x, {% static 'img/my_checks@2x.png'%} 2x"
+            alt="My Checks page" />
     </div>
     <div class="col-sm-4">
         <p>
@@ -162,7 +164,9 @@
     <div class="col-sm-8">
         <img
             class="img-responsive"
-            src="{% static 'img/period_grace.png' %}" alt="Period/Grace Time dialog" />
+            src="{% static 'img/period_grace.png' %}"
+            srcset="{% static 'img/period_grace.png'%} 1x, {% static 'img/period_grace@2x.png'%} 2x"
+            alt="Period/Grace Time dialog" />
     </div>
     <div class="col-sm-4">
         Each check has configurable <strong>Period</strong> and <strong>Grace Time</strong> parameters.
@@ -218,7 +222,9 @@
     <div class="col-sm-8">
         <img
             class="img-responsive"
-            src="{% static 'img/channels.png' %}" alt="Channels page" />
+            src="{% static 'img/channels.png' %}"
+            srcset="{% static 'img/channels.png'%} 1x, {% static 'img/channels@2x.png'%} 2x"
+            alt="Channels page" />
     </div>
     <div class="col-sm-4">
         <p>