Ui improvements (#6651)

* PLT-6691 - Centering emoji in post view

* PLT-6737 - FIxing on hover style for heade icons

* PLT-6768 - Fixing error on profile picture

* PLT-6792 - Fixing link preview image not resizing

* PLT-6793 - User popover position on mobile

webapp/sass/responsive/_mobile.scss

@@ -1549,6 +1549,12 @@
 }
 
 @media screen and (max-width: 480px) {
+    .post {
+        .img-div {
+            max-width: 100%;
+        }
+    }
+
     .nav-tabs {
         margin-top: 1em;