Implement xdg-activation-v1

See https://github.com/swaywm/wlroots/pull/2718.

sway/xdg_activation_v1.c

@@ -0,0 +1,20 @@
+#include <wlr/types/wlr_xdg_activation_v1.h>
+#include "sway/tree/view.h"
+
+void xdg_activation_v1_handle_request_activate(struct wl_listener *listener,
+		void *data) {
+	const struct wlr_xdg_activation_v1_request_activate_event *event = data;
+
+	if (!wlr_surface_is_xdg_surface(event->surface)) {
+		return;
+	}
+
+	struct wlr_xdg_surface *xdg_surface =
+		wlr_xdg_surface_from_wlr_surface(event->surface);
+	struct sway_view *view = xdg_surface->data;
+	if (!xdg_surface->mapped || view == NULL) {
+		return;
+	}
+
+	view_request_activate(view);
+}