The ornamental design for a gameboard, as shown and described.
FIG. 1 is a front perspective view of a game board, showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left side elevation view thereof, the right side elevation is an identical image thereof; and,
FIG. 5 is a top plan view thereof, and the bottom plan view is an identical image thereof.
The evenly sized dash-dash broken lines shown in the drawings depict portions of the game board that form no part of the claimed design.
The unevenly sized dash-dot-dash broken lines shown in the drawings depict the bounds of the claimed design and do not form part of the claimed design.