Add margin bottom to images and videos in the feed

src/app/components/feed/postlist/postlist.component.sass

@@ -60,16 +60,19 @@ $mat-card-header-size: 40px !default
     display: block
     margin-left: auto
     margin-right: auto
+    margin-bottom: 0.5em
   ::ng-deep video
     width: 100%
     max-height: 40vh
     outline: none
     user-select: none
+    margin-bottom: 0.5em
   ::ng-deep audio
     width: 100%
     max-height: 40vh
     outline: none
     user-select: none
+    margin-bottom: 0.5em
 
   .mat-button
     min-width: 32px !important