Keep notifications accessible after they are hidden

[Chealer]

This library does its job really well, except for one thing: remembering past notifications.
By default a notification seems to display for about 5 s, which is reasonable. However, when an error occurs, 5 s is not much time to take notes if it's an unknown, non-trivial error.
Most notification systems deal with this by keeping notifications accessible for a short term, until they are dismissed or the system is restarted. For example, Windows 10 has notifications in the Action Center, macOS has the Notification Center, and KDE has Plasma's notification system, also linked to the system tray.

The main problem for this library is that Angular doesn't come with a task bar where whatever widget to access previous notifications would fit. It's difficult to integrate such a widget in an unknown host application, but I think a bit of configurability could provide results useful in many situations, although there will always be apps which need a custom integration. I believe displaying in the bottom right corner by default would be best, and that giving the option of displaying in any other corner would already cover most cases.

This is a really vague request so that something basic is added, therefore I won't set precise specifications, but here are the main points I suggest or prefer for our situation:

1. Informative notifications would not need to be stored there. I wish that errors would though, at least optionally.
2. The widget would not need to appear before a first persistent notification.
3. The widget could be transparent.
4. The widget could use sticky positioning.
5. Storing the last 5 notifications or those in the last hour would be plenty for us.