Include function to mosaic OBIA results

[EstefaPizarro]

Describe the requested improvement
The segmentation and classification results of the segmented cube are in vector format (.gpkg). This format does not directly allow the observation of a final map or the union of the information of the cube tiles. The possibility of including a rasterization process of this information is requested in order to apply the sits_mosaic() function. In the mosaic function it would be interesting to be able to define the function for the areas with overlapping information, such as mean, median, minimum, maximum, first, last.

I leave an example made with the data from the virtual machine shared with INE Chile
https://gist.github.com/EstefaPizarro/baedc18c9a7c9d643a8a535ded102ea9