The ornamental design for an article of furniture, as shown and described.
FIG. 1 is a front perspective view of an article of furniture embodying the new design;
FIG. 2 is a right side view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a rear view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
FIG. 1 shows portions of the article of furniture in broken lines. The portions shown in broken lines are for environmental purposes only and form no part of the claimed design. Stipple shading is added to convey surface contouring; the stipple shading is not to be understood as conveying a particular surface finish.