Show notification for new blog posts and new post dot in sidebar

...org/briarproject/briar/desktop/blog/BlogPostsReadEvent.kt

...tlin/org/briarproject/briar/desktop/blog/FeedViewModel.kt

...org/briarproject/briar/desktop/navigation/BriarSidebar.kt

...briarproject/briar/desktop/navigation/SidebarViewModel.kt

...riar/desktop/notification/AbstractNotificationProvider.kt

...roject/briar/desktop/notification/NotificationProvider.kt

...t/briar/desktop/notification/SoundNotificationProvider.kt

.../main/kotlin/org/briarproject/briar/desktop/ui/BriarUi.kt

...otlin/org/briarproject/briar/desktop/ui/MessageCounter.kt

...n/org/briarproject/briar/desktop/ui/MessageCounterImpl.kt

...esktop/src/main/resources/strings/BriarDesktop.properties

...org/briarproject/briar/desktop/TestRandomConversations.kt