Cannot pan on y-axis when zoomed and rotated=true

[digEmAll]

Hi All,
in rotated=true charts, when you zoom (using type zoom.type=scroll, because zoom.type=drag doesn't work ) you cannot pan on the y-axis to see the others values.

Check the following jsfiddle:
https://jsfiddle.net/yeo0rkwx/
(zoom using the scroll-wheel then drag vertically: the chart won't move, while doing the same when rotated=false works for the x-axis).

• C3 version: 0.7.18
• D3 version: 5.9.2
• Browser: Chrome 83.0.4103.116, Firefox 77.0.1
• OS: Windows 10

[digEmAll]

Correction: it seems to works if you drag horizontally, i.e. if you drag the mouse horizontally the zoomed chart pans vertically...

[digEmAll]

I created a PR which should fix the issue (my first one, so please be patient 😅)