add at32 to README.rst, rename at32 board to lower case, correct name to match mcu, add meta data

hw/bsp/at32f425/boards/at_start_f425/board.h

@@ -24,6 +24,11 @@
  * This file is part of the TinyUSB stack.
  */
 
+/* metadata:
+   name: AT-START-F425
+   url: https://www.arterychip.com/en/product/AT32F425.jsp
+*/
+
 #ifndef BOARD_H_
 #define BOARD_H_
 

hw/bsp/at32f425/family.c

@@ -24,6 +24,10 @@
  * This file is part of the TinyUSB stack.
  */
 
+/* metadata:
+   manufacturer: Artery
+*/
+
 #include "at32f425_clock.h"
 #include "board.h"
 #include "bsp/board_api.h"