[log] Question: 2 file targets with diffrent filters

- I would like to have possibility to set custom log dir with some default variables, also I would like to see them in documentation.

- and I would like to set subfolders for LogDir like this:

```
tauri_plugin_log::TargetKind::LogDir {
file_name: Some("debug".to_string()),
folder: 'debug/examplel'
},
```