added zoomScale property to centerAction to set zoom level when executing the action

[jonah-iden]

Added a zoomScale property to the CenterAction to explicitly set te zoom level when centering the view.

how to test
in the circlegraph example:

• add following new button to the circlegraph.html file
  <button id="centerZoomed">center and zoom selection</button>
• add following code to the standalone.ts to execute the center action on click

document.getElementById('centerZoomed')!.addEventListener('click', async () => {
    dispatcher.dispatch(CenterAction.create(graph.children.map(el => el.id), {animate: true, zoomScale: 2}))
});

now when clicking the button the center action is executed and zoom level is set to 2.

[dhuebner]

@jonah-iden
Thanks! It works very well.
Btw. there are key bindings for center: 'KeyC', 'ctrlCmd', 'shift' and focus: 'KeyF', 'ctrlCmd', 'shift', maybe we can show them in the circles example. What do you think if we print this short cuts in the right bottom in the same color as © 2017 ? We should probably also change 2017 to © 2017-2023 or just © 2023