add ios chat window border

Signed-off-by: Sahil Yeole <sahilyeole93@gmail.com>

flutter/lib/common/widgets/overlay.dart

@@ -400,6 +400,7 @@ void initState() {
             Container(
               width: _width,
               height: _height,
+              decoration: BoxDecoration(border: Border.all(color: MyTheme.border)),
               child: widget.builder(context),
               ),
             ),