The ornamental design for a rvwindowshade, as shown and described.
FIG. 1 is a perspective view of a RV window shade, showing my new design;
FIG. 2 is a front elevation view thereof, the rear elevation view being the same;
FIG. 3 is a left side elevation view thereof, the right side elevation view being the same;
FIG. 4 is a top plan view thereof, the bottom plan view being the same; and,
FIG. 5 is another perspective view thereof, for clarity of illustration.
The dash-dot broken lines in the drawings depict environment only and form no part of the claimed design. The dash-dash broken lines disclose stitching which forms part of the claimed design.