Hello xarray team

I was trying to implement functionality similar to Scikit Image's view_as_windows, but I was having a hard time with the boundary conditions. I understand this request is very similar to rolling with periodic boundary conditions #2007.

MCVE Code Sample

```python

arr = xr.DataArray(np.arange(4), dims=("x",)) arr.rolling(x=2).construct("roll_x", stride=2) <xarray.DataArray (x: 2, roll_x: 2)> array([[nan, 0.], [ 1., 2.]]) Dimensions without coordinates: x, roll_x ```

Expected Output

It would be nice to be able to easily get an output of: python <xarray.DataArray (x: 2, roll_x: 2)> array([[0., 1.], [2., 3.]]) Dimensions without coordinates: x, roll_x

Possible workarounds

With the upcoming features of pad (#3596) and rolling: periodic (#2011) it is actually not that hard to work around with:

```python arr.pad(x=(1,0)).rolling(x=2).construct("roll_x", stride=2).isel(x=slice(1,None))

or

arr.roll(x=-1).rolling(x=2, boundary="periodic").construct("roll_x", stride=2) ```

Idea

Would it be possible to add a keyword argument to either rolling() or construct() that expects an alignment of "left", "right" or "center". I understand that this could break interface copied from Pandas, but I hope it could be useful to others as well.