The ornamental design for a headband, as shown and described.
FIG. 1 is a front view of my headband;
FIG. 2 is a back view of the headband illustrated in FIG. 1;
FIG. 3 is a top view of the headband illustrated in FIG. 1;
FIG. 4 is a bottom view of the headband illustrated in FIG. 1;
FIG. 5 is a side view of the headband illustrated in FIG. 1;
FIG. 6 is a front-side isometric view of the headband illustrated in FIG. 1;
FIG. 7 is a back-side isometric view of the headband illustrated in FIG. 1;
FIG. 8 is a top isometric view of the headband illustrated in FIG. 1, in an assembled configuration;
FIG. 9 is a bottom isometric view of the headband illustrated in FIG. 8;
FIG. 10 is a side view of the headband illustrated in FIG. 1, installed on a human head; and,
FIG. 11 is a front view of the headband illustrated in FIG. 1, installed on a human head.
The broken lines of the headband depict portions of the headband that forms no part of the claim. The partial human figure illustrated by broken lines assists to portray the headband in a position of use and does not form part of the claimed design.