add documentation

crates/valence_protocol/src/item.rs

@@ -44,6 +44,12 @@ impl ItemStack {
  self
  }
 
+ /// This function takes the "Value" of the skin you want to apply to a PlayerHead.
+ /// The "Value" is a Base64-encoded JSON object that is usually provided by websites.
+ /// To learn more: https://minecraft.wiki/w/Item_format#Player_Heads
+ /// 
+ /// # Errors
+ /// This function returns an error if the [ItemStack] you call it on isn't a PlayerHead
  #[must_use]
  pub fn with_playerhead_texture_value(
  mut self,