What is the significance of Tybalt's challenge in Act 2, scene 3? What could it foreshadow?

The significance of Tybalt's challenge can be found in Mercutio's response, which foreshadows Romeo's death.

Alas, poor Romeo! He is already dead, stabbed with a white wench’s black eye, shot through the ear with a love song, the very pin of his heart cleft with the blind bow-boy’s butt shaft.