Chapter 9 Exercise 15. Write a function my implode that works just like the predefined implode (without using implode). In other words, it should be a function of type char list string that takes a list of characters and returns the string containing those same characters in that same order. Hint: since the function is taking a list, applying an action to each item, and returning a single item that is not a list, using foldl or foldr would be a good idea..