Add example of Array slice (#3823)

slice.js

@@ -11,6 +11,12 @@
  * @param {number} [start=0] The start position. A negative index will be treated as an offset from the end.
  * @param {number} [end=array.length] The end position. A negative index will be treated as an offset from the end.
  * @returns {Array} Returns the slice of `array`.
+ * @example
+ *
+ * var array = [1, 2, 3, 4]
+ *
+ * _.slice(array, 2)
+ * // => [3, 4]
  */
 function slice(array, start, end) {
   let length = array == null ? 0 : array.length