Set Initial state for open panels

[NunoCardoso]

Hi.

I want to display a collapse with open panels. The user can close them later.

If I don't set activeKey, collapse will mount with closed panels. If I set activeKey with an array, panels will be open, but I can't close them later.

Maybe an initialActiveKey prop in the Collapse, or maybe a boolean prop for each panel?

EDIT: ok, I saw it now, it's the defaultActiveKey prop that does this.