The ornamental design for a featherhairextension, as shown and described.
FIG. 1 is a perspective view of my new design for a feather hair extension;
FIG. 2 is a right side elevational view of the design of FIG. 1;
FIG. 3 is a left side elevational view of the design of FIG. 1;
FIG. 4 is a top plan view of the design of FIG. 1;
FIG. 5 is a bottom plan elevational view of the design of FIG. 1;
FIG. 6 is a front elevational view of the design of FIG. 1;
FIG. 7 is a rear elevational view of the design of FIG. 1; and,
FIG. 8 is a perspective view of my new design for a feather hair extension showing the feather hair extension as it would appear when worn by an individual wherein the individual forms no part of the instant design.