Merge pull request #17334 from neilhem/media-flex-align

Media vertical align flexbox classes

scss/_media.scss

@@ -6,6 +6,12 @@
   .media-body {
     flex: 1;
   }
+  .media-middle {
+    align-self: center;
+  }
+  .media-bottom {
+    align-self: flex-end;
+  }
 } @else {
   .media {
     margin-top: 15px;