swaybar: add tray interface

swaybar/tray/tray.c

@@ -0,0 +1,21 @@
+#include <cairo.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include "swaybar/bar.h"
+#include "swaybar/tray/tray.h"
+#include "log.h"
+
+struct swaybar_tray *create_tray(struct swaybar *bar) {
+	wlr_log(WLR_DEBUG, "Initializing tray");
+	return NULL;
+}
+
+void destroy_tray(struct swaybar_tray *tray) {
+}
+
+void tray_in(int fd, short mask, void *data) {
+}
+
+uint32_t render_tray(cairo_t *cairo, struct swaybar_output *output, double *x) {
+	return 0; // placeholder
+}