message: docs: update README to mention battery option in config
diff: @@ -393,6 +393,7 @@ These are the following supported flag config values:
  | `basic` | Boolean |
  | `hide_table_count`| Boolean |
  | `use_old_network_legend`| Boolean |
  +| `battery` | Boolean |
  | `rate` | Unsigned Int (represents milliseconds) |
  | `default_time_value` | Unsigned Int (represents milliseconds) |
  | `time_delta` | Unsigned Int (represents milliseconds) |
  