The ornamental design for the design for a shadestructure, as shown and described.
FIG. 1 is a top perspective view of a shade structure;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a back view thereof;
FIG. 6 is a left side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken lines depict the bounds of the Claim. The broken away symbols in the drawings indicate that the appearance of any portion of the article between the break lines forms no part of the claimed design.