An enum that specifies what to do when a URL opened through an OpenLink is closed.
When a link is opened, the client either forgets about it or waits until the window is closed.
The implementation depends on the client platform capabilities. OnClose may cause OpenAs to be ignored; if the client platform cannot support both selected values together,
OnClose takes precedence.
Do nothing on close. Default.
Reloads the add-on on when the window closes.
If OpenAs.OVERLAY is also set, then the main card is blocked until the overlay
window is closed and the add-on has finished reloading.
Reload the add-on on closing the URL. This action differs from RELOAD in that it does
not block the main card while showing an OpenAs.OVERLAY window.