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
