Fixed #55 with `zr_window_set_focus` not working

While setting a window to active `zr_window_set_focus` did not
transfer the window on top of the window stack. This wrong
behavior should now be fixed and do what it is supposed to do.

zahnrad.c

@@ -8136,6 +8136,10 @@ zr_window_set_focus(struct zr_context *ctx, const char *name)
     title_len = (int)zr_strsiz(name);
     title_hash = zr_murmur_hash(name, (int)title_len, ZR_WINDOW_TITLE);
     win = zr_find_window(ctx, title_hash);
+    if (ctx->end != win) {
+        zr_remove_window(ctx, win);
+        zr_insert_window(ctx, win);
+    }
     ctx->active = win;
 }
 

zahnrad.h

@@ -1979,4 +1979,3 @@ void zr_menu_end(struct zr_context*);
 #endif
 
 #endif /* ZR_H_ */
-