I claim the ornamental design for a tool hanger, as shown and described.
FIG. 1 is a front elevational view of a tool hanger showing my new design;
FIG. 2 is a right side elevational view thereof, the left side being a mirror image of that shown;
FIG. 3 is a top plan view thereof; and,
FIG. 4 is a front elevational view thereof, with the broken line disclosure of a sample tool being for illustrative purposes only and forming no part of the claimed design.