feat: add header position support to dockview group panel

[mslxl]

Resolve #894

Add headerPosition option to DockviewGroupPanel so that the user can change the position of the tab container in Dockview.

I have added a new action to packages\docs\sandboxes\react\dockview\demo-dockview, which allows the position field to loop through 'top', 'left', 'bottom', and 'right'.

Position	Image
top
left
bottom
right

Tested on firefox and chrome

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 30ccca0:

Sandbox	Source
customheader-dockview	Configuration
dockview-app	Configuration
editor-gridview	Configuration
externaldnd-dockview	Configuration
fullwidthtab-dockview	Configuration
iframe-dockview	Configuration
keyboard-dockview	Configuration
nativeapp-dockview	Configuration
rendering-dockview	Configuration

[mslxl]

Umm, the result of codesandbox is different from my local environment. I am not familiar with codesandbox-ci. Is the CI configured right, or is there something wrong with me?

Here is the result of nativeapp-dockview in my local environment(I run it by modifying the ExampleFrame component):

Besides, if I omit some subtle detail or screwed up some features exists before, please tell me so I can fix it.

[SeanBannister]

This is fantastic and I'm really keen for it, could I suggest changing the orientation of the left tabs:

[AliFlux]

Nice! Cant wait for it to merge