The ornamental designs for a shirtpocket, as shown and described.
FIG. 1 is a front view of the shirt pocket with the shirt pocket partially open according to the present disclosure.
FIG. 2 is a front view of the shirt pocket with the shirt pocket fully open according to the present disclosure.
FIG. 3 is a side view of the shirt pocket in the closed position according to the present disclosure; and,
FIG. 4 is a front view of the shirt pocket in the closed position according to the present disclosure.
The broken lines showing of the overall shirt is included for the purpose of illustrating environmental structure and forms no part of the claimed design.