feat: add XDG autostart support for automatic application launching

feat: implement demo mode for automated feature showcase
feat: add XEmbed system tray protocol for external application icons
feat: add window snapping to left and right halves
feat: add minimize/restore toggle with Alt+F9 keybinding
docs: update README with new features and configuration details
build: update build system for new autostart and demo modules

build/main.d

@@ -19,7 +19,8 @@ build/main.o: src/main.c include/dwn.h include/config.h include/dwn.h \
  /usr/include/dbus-1.0/dbus/dbus-signature.h \
  /usr/include/dbus-1.0/dbus/dbus-syntax.h \
  /usr/include/dbus-1.0/dbus/dbus-threads.h include/systray.h \
- include/news.h include/applauncher.h include/ai.h include/util.h
+ include/news.h include/applauncher.h include/ai.h include/autostart.h \
+ include/demo.h include/util.h
 include/dwn.h:
 include/config.h:
 include/dwn.h:
@@ -53,4 +54,6 @@ include/systray.h:
 include/news.h:
 include/applauncher.h:
 include/ai.h:
+include/autostart.h:
+include/demo.h:
 include/util.h: