Add device event receiver

Create a separate component to handle device events, managed by the
controller.

app/src/receiver.h

@@ -0,0 +1,32 @@
+#ifndef RECEIVER_H
+#define RECEIVER_H
+
+#include <stdbool.h>
+#include <SDL2/SDL_mutex.h>
+#include <SDL2/SDL_thread.h>
+
+#include "net.h"
+
+// receive events from the device
+// managed by the controller
+struct receiver {
+    socket_t control_socket;
+    SDL_Thread *thread;
+    SDL_mutex *mutex;
+};
+
+bool
+receiver_init(struct receiver *receiver, socket_t control_socket);
+
+void
+receiver_destroy(struct receiver *receiver);
+
+bool
+receiver_start(struct receiver *receiver);
+
+// no receiver_stop(), it will automatically stop on control_socket shutdown
+
+void
+receiver_join(struct receiver *receiver);
+
+#endif