The ornamental design for an electronickeyboard, as shown and described.
FIG. 1 is a perspective view of the front, top and right side of an electronic keyboard according to my 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 plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken line showing of the electronic keyboard is included for the purpose of illustrating portions of the electronic keyboard and forms no part of the claimed design.