We claim the ornamental design for an appliance door, as shown and described.
FIG. 1 is a front perspective view of the appliance door showing our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a side elevational view thereof;
FIG. 4 is an opposite side elevational view thereof;
FIG. 5 is the top plan view thereof; and,
FIG. 6 is the bottom plan view thereof.
The rear elevational view is not shown and forms no part of the claimed design. The portion shown in broken lines is for illustrative purposes only and forms no part of the claimed design.