The ornamental design for a hanging basket, as shown and described.
FIG. 1 is a perspective view of the hanging basket with a wire hanger shown in broken lines are for illustrative purposes only and form no part of the claimed design;
FIG. 2 is a top plan view of the hanging basket of my design;
FIG. 3 is a front elevational view of the hanging basket of my design, the rear, right and left side views being identical; and,
FIG. 4 is a bottom plan view of the hanging basket of my design.