Fix ordered list with nest

[thinca]

With below markdown:

1. foo1
2. foo2
    1. bar
        1. buz
3. qux

I expect the following result:

              1      foo1

              2      foo2

                     1      bar

                            1      buz

              3      qux

However, in actual:

              0      foo1

              1      foo2

                     1      bar

                            1      buz

              2      qux

This PR fix this behavior.

[sunaku]

Thanks! 👍 Merged. 🙇

[sunaku]

Hey @thinca, sorry for the long delay: 😅 I have finally released this fix in version 5.1.2 now. 🎉