Added documentation to remove_item

src/libcollections/vec.rs

@@ -1296,7 +1296,18 @@ impl<T: PartialEq> Vec<T> {
     pub fn dedup(&mut self) {
         self.dedup_by(|a, b| a == b)
     }
-
+
+    /// Removes the first instance of `item` from the vector if the item exists.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut vec = vec![1, 2, 3, 1];
+    ///
+    /// vec.remove_item(&1);
+    ///
+    /// assert_eq!(vec, vec![2, 3, 1]);
+    /// ```
     #[unstable(feature = "vec_remove_item", reason = "recently added", issue = "38143")]
     pub fn remove_item(&mut self, item: &T) -> Option<T> {
         let pos = match self.iter().position(|x| *x == *item) {