refine error message when duplicate contact is input

src/views/ContactsView.vue

@@ -587,12 +587,19 @@ export default class ContactsView extends Vue {
       })
       .catch((err) => {
         console.error("Error when adding contact to storage:", err);
+        let message = "An error prevented this import.";
+        if (
+          err.message?.indexOf("Key already exists in the object store.") > -1
+        ) {
+          message =
+            "A contact with that DID is already in your contact list. Edit them directly below.";
+        }
         this.$notify(
           {
             group: "alert",
             type: "danger",
             title: "Contact Not Added",
-            text: "An error prevented this import.",
+            text: message,
           },
           -1,
         );