Add an opt-in filter update notification

[dnovitskyi]

Description

Some users would like to receive a confirmation each time AdGuard successfully updates its filters and userscripts. They'd like the app to show notification each time it happens.

Proposed solution

Add an option (under AdGuard > Settings > General) to show a toast notification each time AdGuard updates filters (both automatically and when prompted via tray icon right-click; clicking on filter update button in main UI already shows a dedicated window). Make it disabled by default, but let the users know that they can enable it (either during onboarding or as a one-time notification.

Alternate solution

None.

Helpdesk ID

Z506128

[Aydinv13]

Will be considered and implemented by next release version