fix(UI): Set refresh indicator colour to accent colour (#454)

assets/design/AppIcon.psd

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:dbd493a957c6bace8782075fbc1e22fafccf6cf2780a5f0880835ce4aa0ebaa9
+size 44027413

lib/core/ui/refresh_indicator.dart

@@ -9,6 +9,7 @@ class LunaRefreshIndicator extends RefreshIndicator {
   }) : super(
           key: key,
           backgroundColor: Theme.of(context).primaryColor,
+          color: Theme.of(context).accentColor,
           onRefresh: onRefresh,
           child: child,
         );