[BUG] Reading VTU only gets last piece

[cbosoft]

Describe the bug
Reading a VTU file only gives the cells from the last piece.

To Reproduce
A minimal code example that reproduces the problem would be a big help if you can provide it. Attach a small mesh file if necessary.

Open a VTU file with multiple pieces. mesh.cells will show only a single piece

I've tracked the issue to a small typo in src/meshio/vtu/_vtu.py, function _organize_cells lines 154 and 155 need indenting in once more to be within the loop above.

        for offset, cls, cdr in zip(point_offsets, cells, cell_data_raw):
            cls, cell_data = vtk_cells_from_data(
                cls["connectivity"].ravel(),
                cls["offsets"].ravel(),
                cls["types"].ravel(),
                cdr,
            )

        for c in cls:
            out_cells.append(CellBlock(c.type, c.data + offset))

to become

        for offset, cls, cdr in zip(point_offsets, cells, cell_data_raw):
            cls, cell_data = vtk_cells_from_data(
                cls["connectivity"].ravel(),
                cls["offsets"].ravel(),
                cls["types"].ravel(),
                cdr,
            )

            for c in cls:
                out_cells.append(CellBlock(c.type, c.data + offset))

Let me know if you want me to draft a PR or anything.