Enable draggable annotations

[stockiNail]

We could happen that a user would like to move the annotations in an empty space on the chart in order to see the underlying data.

To enable that, we could add a new draggable option to the annotation that if is set to true, the user can drag the annotation (or annotations).

mousedown and mouseup event types should be added by the user in order to activate it.
The reset and the fallback to original position can be easily performed by a chart.update() to invoke externally (by a button or another controller).

[kurkle]

Should be almost as easy with an external plugin, so not sure if that is something that should be implementer. Always good to give examples though, so maybe a sample implementation instead?

[stockiNail]

I'm not sure if it could be easy because the plugin is not exposing the elements. I'll do an example in codepen soon.

[stockiNail]

Here codepen: https://codepen.io/stockinail/pen/OJOBEGm

You can drag the labels.

EDIT: added button to reset the drag.

[stockiNail]

@kurkle today I had time to think more about this enhancement. Well, finally I think you are right! This can be done by another plugin.
If you think it could be helpful, I'd like to prepare a codepen to show the implementation. And then, if you agree, I could add a sample in the interactions section. Let me know what you think.

[stockiNail]

Codepen (drag with external plugin) https://codepen.io/stockinail/pen/jOZPWXy