feat: Add media thumbnail support

Author: bilta-keyvalue

src/types.ts

@@ -29,6 +29,7 @@ export interface NotificationDataType {
     subHeader: string;
     body: string;
     actionUrl: string;
+    thumbnailUrl?: string | null;
     avatar: {
       imageUrl: string;
       actionUrl: string | null;
@@ -156,6 +157,7 @@ type Message = {
   subHeader: string;
   body: string;
   actionUrl: string;
+  thumbnailUrl?: string | null;
   avatar: {
     imageUrl: string;
     actionUrl: string | null;