Add related function for each module. [closes #2932]

flattenDepth.js

@@ -9,6 +9,7 @@ import toInteger from './toInteger.js';
  * @param {Array} array The array to flatten.
  * @param {number} [depth=1] The maximum recursion depth.
  * @returns {Array} Returns the new flattened array.
+ * @see flatMap, flatMapDeep, flatMapDepth, flattenDeep
  * @example
  *
  * const array = [1, [2, [3, [4]], 5]];