Fix: fix Android chrome mobile not rendering html <video> element (flutter-webrtc#1938)

There is an issue in chrome mobile where, if the video element tag is
outside of the visible viewport, the video won't be rendered (will
appear as black).

That can happen if the added video tag just happens to go in the bottom
of a body, and whatever relative elements exists before pushes it
outside of the viewport boundary


https://github.com/user-attachments/assets/a0ef4506-7642-4fbd-a68e-dfc0d3798d5c


This fix forces the position html video element (that is already an
absoltue element) to be on the top left so it stays on screen and thus
is rendered by chrome mobile not depending of the contents of the html
itself.

---

I've tested this and it only happens specifically in Androrid-Chrome
combo

cc @kNoAPP that helped find where in the code the html element was
created

Author: dganzella

lib/src/web/rtc_video_renderer_impl.dart

@@ -347,6 +347,8 @@ class RTCVideoRenderer extends ValueNotifier<RTCVideoValue>
       element.style.pointerEvents = "none";
       element.style.opacity = "0";
       element.style.position = "absolute";
+      element.style.left = "0px";
+      element.style.top = "0px";
     }
   }