feedbackd: Support visual feedback via LEDs

Currently all LED feedbacks are infinite we can improve that
later on by using the 'repeat' attribute of the LED pattern
trigger.

src/fbd-dev-leds.h

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2020 Purism SPC
+ *
+ * SPDX-License-Identifier: GPL-3.0+
+ */
+#pragma once
+
+#include "fbd-feedback-led.h"
+
+#include <glib-object.h>
+#include <gudev/gudev.h>
+
+G_BEGIN_DECLS
+
+#define FBD_TYPE_DEV_LEDS (fbd_dev_leds_get_type ())
+
+G_DECLARE_FINAL_TYPE (FbdDevLeds, fbd_dev_leds, FBD, DEV_LEDS, GObject);
+
+FbdDevLeds *fbd_dev_leds_new (GError **error);
+gboolean    fbd_dev_leds_start_periodic (FbdDevLeds *self,
+                                         FbdFeedbackLedColor color,
+                                         guint max_brighness, guint freq);
+gboolean    fbd_dev_leds_stop (FbdDevLeds         *self,
+                               FbdFeedbackLedColor color);
+
+G_END_DECLS