FIG. 1 is a side perspective view of a cart showing my new design; FIG. 2 is a top plan view thereof; FIG. 3 is a rear elevation view thereof; FIG. 4 is a side elevation view thereof; FIG. 5 is a front elevation view thereof; and, FIG. 6 is a bottom plan view thereof. The broken line shown in FIGS. 1-6 are for illustrative purposes only and forms no part of the claimed design.