The ornamental design of a wirelesskeyboard, as shown and described.
FIG. 1 is a perspective view of a wireless keyboard;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a top end view thereof;
FIG. 5 is a side view thereof;
FIG. 6 is an opposite side view thereof;
FIG. 7 is a bottom view thereof;
FIG. 8 is a perspective view of a second embodiment thereof, the broken lines showing illustrated portions of the keyboard and form no part of the claimed design;