The ornamental design for a showerhead, as shown and described.
FIG. 1 is a left side elevational view of a showerhead according to the invention.
FIG. 2 is a right side elevational view of the showerhead of FIG. 1.
FIG. 3 is a front elevational view of the showerhead of FIG. 1.
FIG. 4 is a rear elevational view of the showerhead of FIG. 1.
FIG. 5 is a top plan view of the showerhead of FIG. 1.
FIG. 6 is a bottom plan view of the showerhead of FIG. 1; and,
FIG. 7 is a three-quarter perspective view of the showerhead of FIG. 1.
The dashed lines illustrate environment that does not form a part of the present invention, and no claim is made to the material illustrated with dashed lines.