explorer: explain how to fix error

src/explorer/fileNameFormGroup/translations/en.json

@@ -7,6 +7,6 @@
         "hasFileExtension": "The file extension will be added automatically.",
         "hasInvalidFirstCharacter": "File name must start with a letter ({letters}) or underscore ({underscore}).",
         "hasInvalidCharacters": "File name can only contain letters ({letters}), numbers ({numbers}), dashes ({dash}) and underscores ({underscore}).",
-        "alreadyExists": "A file with this name already exists."
+        "alreadyExists": "A file with this name already exists. Try a different name."
     }
 }