The ornamental design for a touchkey, as shown and described.
FIG. 1 is a perspective view of a touch key showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof;
FIG. 8 is an enlarged view of an indicated portion 8 in FIG. 2; and,
FIG. 9 is a top view thereof shown on a QWERTY keyboard.
The broken lines shown in FIGS. 1, 6, 7, and 9 that are immediately adjacent to the shaded areas represent the bounds of the claimed design, while all other lines are directed to environment and form no part of the claimed design.