fix(VideoLoader): autoplay issue in safari on ios and osx

When controls attribute is not specified video autoplay is behaviour becomes flaky. After testing it
appears that this maybe due to the poster property of the video element and how the property is
being set. Setting the poster attribute rather than the property seems to resolve the issue

Author: edoparearyee

src/app/video-loader/video-loader/video-loader.component.html

@@ -2,7 +2,7 @@
   *ngIf="video"
   [src]="src"
   [class]="videoClass"
-  [poster]="poster"
+  [attr.poster]="poster"
   [autoplay]="autoplay"
   [loop]="loop"
   [muted]="muted"