make targets "loadable"

components/targets/targets.h

@@ -0,0 +1,22 @@
+/* 
+ *  Squeezelite for esp32
+ *
+ *  (c) Sebastien 2019
+ *      Philippe G. 2019, philippe_44@outlook.com
+ *
+ *  This software is released under the MIT License.
+ *  https://opensource.org/licenses/MIT
+ *
+ */
+ 
+#pragma once 
+ 
+#include "stddef.h" 
+#include "stdbool.h" 
+
+struct target_s {
+	char *model;
+	bool (*init)(void);
+};
+
+extern const struct target_s target_muse;