[feature] Add Counts to the Sidebar/Drawer

[tarcinil]

It would be nice to have entity/check/silence count for the items in the drawer.

[additional] it would be nice to have a hover flyout as well.

This would also be a feature parity with uchiwa.

Feature Suggestion

When I look at my uchiwa dashboard sidebar, I see the number of event/entities/checks/silences/etc.

This is requesting the same item into this system.

Possible Implementation

N/A

Context

This is to allow feature parity with the previous system. It also allows for a quick glance to know the high-level state of of system without having to browse through various pages.