config: enhance the configuration file with comments

src/wireplumber.conf

+# Basic pipewire integration - do not remove
 load-module C libwireplumber-module-pipewire
+
+# Grants access to security confined clients
+load-module C libwireplumber-module-client-permissions
+
+# Endpoint implementation for standard audio devices
+# using software conversions, mixing and volume controls
 load-module C libwireplumber-module-pw-audio-softdsp-endpoint
+
+# Endpoint that provides high-level volume controls for the AGL mixer
+load-module C libwireplumber-module-mixer
+
+# Monitors the ALSA devices that are discovered via udev
+# and creates softdsp-endopints for each one of them
 load-module C libwireplumber-module-pw-alsa-udev
+
+# Implements linking clients to devices and maintains
+# information about the devices to be used.
+# If you want to override the default audio devices,
+# comment the first line and uncomment the lines below
 load-module C libwireplumber-module-simple-policy
-load-module C libwireplumber-module-mixer
-load-module C libwireplumber-module-client-permissions
+#load-module C libwireplumber-module-simple-policy {
+#  "default-playback-device": <"hw:0,0">,
+#  "default-capture-device": <"hw:0,0">
+#}