The ornamental design for a badge, as shown and described.
FIG. 1 is a perspective view of a badge showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a side elevational view thereof, the opposite side being a mirror image;
FIG. 4 is a top plan view thereof; and,
FIG. 5 is a rear elevational view thereof.