fix: strict movetype moving wrong panel on circular flicking

[malangfox]

Issue

#841

Details

When using the next Panel to move in moveType: strict, we use the following rules

1. find the anchorAtPosition that is closest to the point the camera is currently showing.
2. if anchorAtPosition is not the same as Flicking's current Panel, we move to anchorAtPosition.
3. if anchorAtPosition is the same as Flicking's current Panel, navigate to adjacentAnchor which is the next/prev anchor of anchorAtPosition.

However, there is an exception to this rule that can cause an error when you rotate the circular Flicking once before the event that updates the current panel is fired,

If you rotate the Flicking once, you'll end up in a situation where the camera is showing the position of the current panel again.

If that happens, you won't be able to stop on that panel by step 3 and you'll move to the next Anchor.
This will cause the error described in the issue.

In this PR, I have fixed moveType: strict to continuously update the current Panel based on the willChange event to prevent the above exception from occurring.

[coveralls]

coverage: 82.638% (-0.001%) from 82.639%
when pulling 044b725 on malangfox:fix-circular-strict-panels
into 346c43a on naver:master.