Add libi3/load_font, use it everywhere

…except for i3bar, which needs slightly more information about the font

include/config.h

@@ -20,6 +20,7 @@
 #include <stdbool.h>
 #include "queue.h"
 #include "i3.h"
+#include "libi3.h"
 
 typedef struct Config Config;
 typedef struct Barconfig Barconfig;