Add string representation for rio accessor

[remi-braun]

Adding a quick string representation for the rio accessor.

Example for /app/test/test_data/input/veris.nc

rioxarray accessor (.rio) | RasterDataset
Variables:
        Name: 'Slope'
        'Slope' attributes:
                count: 1
                crs: 4326
                rasterio_dtype: float64
                nodata: -9999.0
                transform: | 0.00, 0.00,-94.30|
| 0.00,-0.00, 42.35|
| 0.00, 0.00, 1.00|
                height: 50
                width: 35
                blockxsize: 35
                blockysize: 1
                bounds: (-94.30306000000002, 42.350229999999996, -94.30271000000002, 42.350730000000006)
        Name: 'Red'
        'Red' attributes:
                count: 1
                crs: 4326
                rasterio_dtype: float64
                nodata: -9999.0
                transform: | 0.00, 0.00,-94.30|
| 0.00,-0.00, 42.35|
| 0.00, 0.00, 1.00|
                height: 50
                width: 35
                blockxsize: 35
                blockysize: 1
                bounds: (-94.30306000000002, 42.350229999999996, -94.30271000000002, 42.350730000000006)

[remi-braun]

This helps to quickly grasp the dataset information, a bit like printing ds.meta in rasterio