doc: make all manpages with Doxygen

Use (fixed-up) Doxygen manpage output for all program & module manpages.

This also allows formatting the manual pages properly in the HTML docs.

The Markdown pages work properly only with Doxygen >= 1.9.7, older
versions put them to wrong place in the HTML docs.

doc/dox/programs/pw-mon.1.md

@@ -0,0 +1,36 @@
+\page page_man_pw-mon_1 pw-mon
+
+The PipeWire monitor
+
+# SYNOPSIS
+
+**pw-mon** \[*options*\]
+
+# DESCRIPTION
+
+Monitor objects on the PipeWire instance.
+
+# OPTIONS
+
+\par -r | \--remote=NAME
+The name the *remote* instance to monitor. If left unspecified, a
+connection is made to the default PipeWire instance.
+
+\par -h | \--help
+Show help.
+
+\par \--version
+Show version information.
+
+\par -N | \--color=WHEN
+Whether to use color, one of 'never', 'always', or 'auto'. The default
+is 'auto'. **-N** is equivalent to **--color=never**.
+
+# AUTHORS
+
+The PipeWire Developers <$(PACKAGE_BUGREPORT)>;
+PipeWire is available from <$(PACKAGE_URL)>
+
+# SEE ALSO
+
+\ref page_man_pipewire_1 "pipewire(1)"