The ornamental design for a swingcart for child, as shown and described.
FIG. 1 shows a perspective view of the present design.
FIG. 2 shows a front view of the present design.
FIG. 3 shows a rear view of the present design.
FIG. 4 shows a left view of the present design.
FIG. 5 shows a right view of the present design.
FIG. 6 shows a top view of the present design; and,
FIG. 7 shows a bottom view of the present design.
The broken line showing of reinforcement ribs is for the purpose of illustrating portions of the swing cart for child and forms no part of the claimed design.