The ornamental design for a wifiextender, as shown and described.
FIG. 1 is a front perspective view of a WiFi extender showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The WiFi extender is shown with a symbolic break along its height. The appearance of any portion of the WiFi extender between the adjacent break lines forms no part of the claimed design. The broken lines depicting the remainder of the WiFi extender show features that form no part of the claimed design. The unshaded center circular region on the bottom of the WiFi extender also forms no part of the claimed.