Update SvgDecoder.java since our header tag starts with <?xml not <svg

rocket-chat-android-widgets/src/main/java/chat/rocket/android/widget/fresco/SvgDecoder.java

@@ -24,7 +24,7 @@ public class SvgDecoder {
   public static final ImageFormat SVG_FORMAT = new ImageFormat("SVG_FORMAT", "svg");
 
   // We do not include the closing ">" since there can be additional information
-  private static final String HEADER_TAG = "<svg";
+  private static final String HEADER_TAG = "<?xml";
 
   public static class SvgFormatChecker implements ImageFormat.FormatChecker {
 
@@ -141,4 +141,4 @@ public class SvgDecoder {
       setPicture(mSvg.renderToPicture(bounds.width(), bounds.height()));
     }
   }
-}
+}
\ No newline at end of file