Add timeConverter Property to NotificationView for Custom Time Formatting

[leewyatt]

Description:
The NotificationView class currently uses a default time converter to display dates and times, which is implemented within the ContentPane inner class. This converter formats date-time information in a pre-defined way ("now", "yesterday", "2 days ago", etc.). While this works well for most cases, there is a need to allow users to customize how date and time are formatted based on their specific requirements.

Proposed Feature:
Introduce a timeConverter property in the NotificationView class. This property should allow users to define their own StringConverter implementation, which can then be used across all instances of NotificationView to format date and time information.