Add missing parameter type (#84)

Co-authored-by: Rafa Gómez <rgomezcasas@gmail.com>

src/apply.php

@@ -10,20 +10,20 @@
  * This function tries to solve the problem of calling a function stored in a class attribute, because if you try
  * `$this->callable($arg1, $arg2)` PHP expects `$this->callable` to be a function and not a property. And to avoid
  * use the magic method _invoke_ that will properly work `$this->callable->__invoke($arg1, $arg2)` we use go with
- * `apply($this->callable, $arg1, $arg2)`.
+ * `apply($this->callable, [$arg1, $arg2])`.
  *
  * Be aware that using this function most IDEs will lose the path, so they will not detect that your are passing the
  * wrong number of parameters or will not do as you expect a change of signature. To have a good test suite would be a
  * requirement for a widely use of this function in your code.
  *
  * @param callable $fn   function to be executed
- * @param mixed[]  $args arguments to be passed to the called function
+ * @param iterable $args arguments to be passed to the called function
  *
  * @return mixed
  *
  * @since 0.1
  */
-function apply(callable $fn, $args = [])
+function apply(callable $fn, iterable $args = [])
 {
     return $fn(...to_array($args));
 }