Improve pytest.approx on lists

When a [`pytest.approx`](https://docs.pytest.org/en/7.1.x/reference/reference.html#pytest-approx) with a list of values is failing, current pretty-print is not super readable compared to simple lists:

```py
import pytest

def test_approx():
assert pytest.approx([100, 100, 100], abs=1) == [90, 100, 110]

def test_ints():
assert [100, 100, 100] == [90, 100, 110]
```


Since pytest-icdiff already supports approx on single value, do you think it is a doable improvement of printing list values on separate lines too?

And kudo for the plugin!