Fix various issues detected by html-proofer (#270)

* Add alt tag to the images

Signed-off-by: hossainemruz <hossainemruz@gmail.com>

* Remove unnecessary /

Signed-off-by: hossainemruz <hossainemruz@gmail.com>

layouts/_default/search.html

@@ -43,7 +43,7 @@
             <a href="${link}" class="post-card-link">
               <div class="card" style="min-height: 352px;"><a href="${link}" class="post-card-link">
                 <div class="card-head">
-                  <img class="card-img-top" src="${hero}">
+                  <img class="card-img-top" src="${hero}" alt="Card Heading Image">
                 </div>
                 <div class="card-body">
                   <h5 class="card-title">${title}</h5>