Log wlroots version on startup

Can be useful to make sure a bugfix is included. In the future maybe
the wlroots version string could include a commit hash when built
from source, too.

sway/main.c

@@ -12,6 +12,7 @@
 #include <sys/un.h>
 #include <unistd.h>
 #include <wlr/util/log.h>
+#include <wlr/version.h>
 #include "sway/commands.h"
 #include "sway/config.h"
 #include "sway/server.h"
@@ -344,6 +345,7 @@ int main(int argc, char **argv) {
 	}
 
 	sway_log(SWAY_INFO, "Sway version " SWAY_VERSION);
+	sway_log(SWAY_INFO, "wlroots version " WLR_VERSION_STR);
 	log_kernel();
 	log_distro();
 	log_env();