Fix navigation controller root bug

[CJEkman]

This PR fixes a set of subtle problems experienced when a UINavigationController is presented in a modal context. The initial presentation wasn't performed immediately, and some kind of lifecycle issue caused input cursors for UITextField instances in the first view controller to be missing from the view hierarchy.

The issue could be solved by assigning an explicit root view controller, which lead to the discovery of the problem here in Presentation - likely introduced when creating the workaround for issue #40 in iOS 13+ without considering UINavigationController. This PR also fixes a minor issue found when setting up the dismiss action for these flows.

[nataliq-pp]

Looks like the cancel button doesn't get correctly set up in the case of embedInNavigationController option.
Will be good to add a test case to the StylesAndOptions example project that covers presenting a view controller in an explicit instance of UINavigationController which is what the bug was about.

[nataliq-pp]

Looks good. This will be a patch I suppose. Feel free to bump the version in the same PR. We need to update issue 40 to include the navigation controller too.

[CJEkman]

@nataliq The version is bumped and the changelog has been updated. I also added info to issue #40
Please leave another review 🙂