event-naming-spec: Separate application and system events

Make it obvious which events are meant to be used by "normal" GUI
applications in contrast to system components like desktop shells or
components monitoring the battery, etc.

This was prompted by
https://github.com/flatpak/xdg-desktop-portal/issues/929

doc/Event-naming-spec-0.0.0.md

@@ -51,14 +51,15 @@ name space clashes with future standardized names. Example:
 
 This section describes the standard Event names that should be used
 by artists when creating themes, and by developers when writing
-applications which will use the Feedback Theme Specification.
+applications which will use the Feedback Theme Specification. Application
+developers should only use event names from the *Applications*
+section as the other sections are reserved for system components.
 
-### Alerts
+### Applications
 
-- battery-low: The Event used when the battery is low (below 20%, for example).
-- power-unplug-battery-low: The power cable has been unplugged and the battery level is low.
+These events are meant to be used by applications.
 
-### Notifications
+#### Notifications
 
 - camera-focus: The event used when the camera got focus.
 - camera-shutter: The event used when a photo was taken.
@@ -74,27 +75,46 @@ applications which will use the Feedback Theme Specification.
 - phone-outgoing-busy: The event used when for outgoing phone/voip call when the responder is busy/not available.
 - phone-hangup: The event used when a phone/voip call is hung up.
 - phone-failure: The event used when a phone/voip call is terminated because of a failure.
-- battery-caution: The event used when the battery is nearing exhaustion (below 40%, for example).
-- battery-full:	The event used when the battery is fully loaded up.
-- device-added: The event used when a device has become available to the desktop, i.e. due to USB plugging.
-- power-plug: The power cable has been plugged in.
-- power-unplug: The power cable has been unplugged.
 - alarm-clock-elapsed: A user configured alarm elapsed.
 - timeout-completed: A user configured timeout completed (e.g. a stop watch).
 
-### Actions
+#### Actions
 
 - message-sent-instant: The sound used when a new IM is sent.
+
+#### Input Events
+
+- button-pressed:	The event used when a button is pressed.
+- button-released:  The event used when a button is released.
+
+### System Components
+
+These events are meant to be used by applications.
+
+### Actions
+
 - bell-terminal: The sound to use as a terminal bell.
 - theme-demo: A event that should be played for demoing this theme. Usually
   this should just be an alias for a very representative sound (such as
   a incoming phone call) of a theme that would work nicely as a demo event for
   a theme in the theme selector dialog.
 
-### Input Event
+### Alerts
+
+- battery-low: The Event used when the battery is low (below 20%, for example).
+- power-unplug-battery-low: The power cable has been unplugged and the battery level is low.
+
+### Notifications
+
+- battery-caution: The event used when the battery is nearing exhaustion (below 40%, for example).
+- battery-full:	The event used when the battery is fully loaded up.
+- device-added: The event used when a device has become available to the desktop, i.e. due to USB plugging.
+- power-plug: The power cable has been plugged in.
+- power-unplug: The power cable has been unplugged.
+
+#### Input Events
 
-- button-pressed:	The event used when a button is pressed.
-- button-released:  The event used when a button is released.
 - window-close:     The sound used when an existing window is closed.
 
+
 [Sound naming spec]: http://0pointer.de/public/sound-naming-spec.html