The `push()` function appends the given argument(s) to the end of the given array
while maintaining their order.

Returns the last pushed value.

Returns `null` if the given destination argment is not an array.

Throws a type exception if the given array is immuatable.

-- Testcase --
{%
	let arr = [];

	printf("%.J\n", [
		// push one element
		push(arr, 123),

		// push multiple elements
		push(arr, 1, 2, 3),

		// push null values
		push(arr, null, null, 4),

		// push no-op
		push(arr),

		// push with invalid destination
		push({}, 1, 2, 3)
	]);

	printf("%.J\n", arr);
%}
-- End --

-- Expect stdout --
[
	123,
	3,
	4,
	null,
	null
]
[
	123,
	1,
	2,
	3,
	null,
	null,
	4
]
-- End --