Fix battery status changes not being detected

Historically we listened to /sys/class/poewr_supply inotify events,
which does not seem to work anymore.
We switched now to udev netlink kernel events.

include/util/udev_deleter.hpp

@@ -0,0 +1,21 @@
+#pragma once
+
+#include <libudev.h>
+
+namespace waybar::util {
+struct UdevDeleter {
+  void operator()(udev *ptr) const { udev_unref(ptr); }
+};
+
+struct UdevDeviceDeleter {
+  void operator()(udev_device *ptr) const { udev_device_unref(ptr); }
+};
+
+struct UdevEnumerateDeleter {
+  void operator()(udev_enumerate *ptr) const { udev_enumerate_unref(ptr); }
+};
+
+struct UdevMonitorDeleter {
+  void operator()(udev_monitor *ptr) const { udev_monitor_unref(ptr); }
+};
+}  // namespace waybar::util