added minimal error handling and user feedback

lib/l10n/app_de.arb

@@ -30,8 +30,14 @@
     "import": "Importieren",
     "activateJsonExport": "Immer als JSON speichern",
 
+    "@@comment": "Info",
+    "exportSuccess": "Daten exportiert",
+    "importSuccess": "Daten importiert",
+
     "@@comment": "Errors",
     "errorStoragePermisson": "Zugriff auf Speicher verwehrt",
     "errorCouldNotLaunchUrl": "Konnte Url nicht öffnen",
-    "errorInvalidUrl": "Fehlerhafte Url"
+    "errorInvalidUrl": "Fehlerhafte Url",
+    "exportFailed": "Export fehlgeschlagen",
+    "importFailed": "Import fehlgeschlagen"
 }

lib/l10n/app_en.arb

@@ -29,9 +29,16 @@
     "export": "Export",
     "import": "Import",
     "activateJsonExport": "Always save to JSON",
+
+    
+    "@@comment": "Info",
+    "exportSuccess": "Exported data",
+    "importSuccess": "Imported data",
     
     "@@comment": "Errors",
     "errorStoragePermisson": "Storage permissions denied",
     "errorCouldNotLaunchUrl": "Could not launch Url",
-    "errorInvalidUrl": "Invalid Url"
+    "errorInvalidUrl": "Invalid Url",
+    "exportFailed": "Export failed",
+    "importFailed": "Import failed"
 }