The ornamental design for a stringlight, as shown and described.
FIG. 1 is a front perspective view of a string light, showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a top side view thereof;
FIG. 5 is a bottom side view thereof;
FIG. 6 is a right view thereof;
FIG. 7 is a left view thereof;
FIG. 8 is a partial enlarged view of FIG. 1;
FIG. 9 is a partial enlarged view of FIG. 3; and,
FIG. 10 is a partial enlarged view of FIG. 7.
The broken lines in the drawings illustrate the portions of the string light, which form no part of the claimed design. The dash-dot-dash broken lines encircling the enlarged views are for annotative purposes only and form no part of the claim thereof.