The ornamental design for a stemwareholder, as shown and described.
FIG. 1 is a perspective view of a stemware holder showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a front plan view thereof;
FIG. 5 is a side plan view thereof;
FIG. 6 is a front plan view illustrating the stemware holder holding a piece of stemware in the upright position; and,
FIG. 7 is a front plan view illustrating the stemware holder holding a piece of stemware in the inverted position.
The broken line showing of the stemware in FIGS. 6 and 7 is for the purpose of illustrating the environment related to the claimed design and forms no part of the claimed design.