message: added root_group function
diff: @@ -15,7 +15,7 @@ use crate::utils::{_last_cpl_err, _last_null_pointer_err, _path_to_c_string, _st
  use crate::vector::{sql, Geometry, OwnedLayer};
  use crate::{
  gdal_major_object::MajorObject, raster::RasterBand, spatial_ref::SpatialRef, vector::Layer,
  - Driver, Metadata,
  + Driver, Metadata, raster::mdarray::Group
  };
  use gdal_sys::OGRGeometryH;
  use gdal_sys::{
  @@ -414,6 +414,15 @@ impl Dataset {
  Ok(RasterBand::from_c_rasterband(self, c_band))
  }
  }
  + pub fn root_group(&self) -> Result<Group> {
  + unsafe {
  + let c_group = gdal_sys::GDALDatasetGetRootGroup(self.c_dataset());
  + if c_group.is_null() {
  + return Err(_last_null_pointer_err("GDALGetRasterBand"));
  + }
  + Ok(Group::from_c_group(self, c_group))
  + }
  + }
  /// Builds overviews for the current `Dataset`. See [`GDALBuildOverviews`].
  ///
  