The ornamental design for a foldableshelf, as shown and described.
FIG. 1 is a left side elevation view of a foldable shelf in the unfolded position showing my design;
FIG. 2 is front elevation view thereof;
FIG. 3 is right side elevation view thereof;
FIG. 4 is back elevation view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a left side elevation of a foldable shelf in the folded position showing my design;
FIG. 7 is a perspective view thereof;
FIG. 8 is a upper perspective view of a foldable shelf in the unfolded position showing my design;
FIG. 9 is a lower perspective view thereof;
FIG. 10 is lower perspective view of a foldable shelf in the open position in which the left shelf support and the right shelf support are pivoted in the stored position; and,
FIG. 11 is a lower perspective view of a foldable shelf in the open position in which the left shelf support is in a deployed position and the right shelf support is in the stored position.