The ornamental design for a headgarment, as shown and described.
FIG. 1 is a perspective view of a head garment showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a side view thereof;
FIG. 5 is another side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a perspective view thereof in condition of use.
The broken lines in the figures show portions of the head garment, which form no part of the claimed design. The additional broken lines shown in FIG. 8 are to show environment and form no part of the claimed design.