Count of clients should be visible when on monocle layout

[pm4rcin]

Hi, in DWM the count of clients on given tag is visible when on monocle and there's more than 1 window. Since we want to achieve parity it should be implemented. Also if I recall correctly for >9 it's 9+.

[yveszoundi]

I implemented the feature as it exists in dwm:

• The client count is displayed when greater than zero for the monocle layout
• @pm4rcin, per latest dwm code, the client count is displayed "as is" even when greater than 9

This has been tested with somebar and dwlb as status bars, and I assume that it works pretty much the same with yambar , waybar or any other bars that support dwl.