Add alt attributes

Author: adpi2

_includes/online-courses-box.html

@@ -2,7 +2,7 @@
   <div class="online-courses-wrapper">
     <div class="online-courses-image">
       <a href="{{ include.link }}" >
-        <img src="{{ site.baseurl }}/resources/images/online-courses/{{include.image}}"">
+        <img src="{{ site.baseurl }}/resources/images/online-courses/{{ include.image }}" alt="{{ include.image }}">
       </a>
     </div>
     <div class="online-courses-content">