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/pipewire-pulse-modules.7.md

@@ -0,0 +1,32 @@
+\page page_man_pipewire-pulse-modules_7 pipewire-pulse-modules
+
+PipeWire Pulseaudio modules
+
+# DESCRIPTION
+
+PipeWire's Pulseaudio emulation implements several Pulseaudio modules.
+It only supports its own built-in modules, and cannot load external
+modules written for Pulseaudio.
+
+The built-in modules can be loaded using Pulseaudio client programs, for
+example `pactl load-module \<module-name\> \<module-options\>`.
+They can also added to `pipewire-pulse.conf`, typically by a
+drop-in file in `~/.config/pipewire/pipewire-pulse.conf.d/`
+containing the module name and its arguments
+
+    pulse.cmd = [
+       { cmd = "load-module" args = "module-null-sink sink_name=foo" flags = [ ] }
+    ]
+
+# KNOWN MODULES
+
+$(PIPEWIRE_PULSE_MODULES)
+
+# AUTHORS
+
+The PipeWire Developers <$(PACKAGE_BUGREPORT)>;
+PipeWire is available from <$(PACKAGE_URL)>
+
+# SEE ALSO
+
+\ref page_man_pipewire-pulse_1 "pipewire-pulse(1)"