PLT-5521: Mandatory version in line 1 of bulk import. (#5400)

i18n/en.json

@@ -2979,6 +2979,14 @@
     "id": "app.import.import_user.save_preferences.error",
     "translation": "Failed to save the provided preferences for the user."
   },
+  {
+    "id": "app.import.process_import_data_file_version_line.invalid_version.error",
+    "translation": "Did not find a valid version type object in the first line of the import data file."
+  },
+  {
+    "id": "app.import.bulk_import.unsupported_version.error",
+    "translation": "The version of the import data file format of the provided file is not supported by this version of Mattermost."
+  },
   {
     "id": "authentication.permissions.create_team_roles.description",
     "translation": "Ability to create new teams"