OSD window switcher, based on work done by @Consolatis,

it uses a custom field (a subset of printf style formatting) to
replace the original field formats. I added documentation, and
fixed the few style check complaints.

Example:

<windowSwitcher preview="no" outlines="no" allWorkspaces="yes">
  <fields>
    <field content="custom" format="foobar %b %3s %-10o %-20W %-10i%t" width="100%" />
  </fields>
</windowSwitcher>

Mono space font recommended, may need osd width adjusted

src/input/keyboard.c

@@ -11,6 +11,7 @@
 #include "input/key-state.h"
 #include "labwc.h"
 #include "menu/menu.h"
+#include "osd.h"
 #include "regions.h"
 #include "view.h"
 #include "workspaces.h"