add micropython demo on bearpi board

board/BearPi_STM32L431RC/KEIL/micropython_basic_demo/scripts/thread.py

@@ -0,0 +1,19 @@
+import _thread
+
+lock = _thread.allocate_lock()
+n_thread = 4
+n_finished = 0
+
+def thread_entry(no):
+    print(no)
+    with lock:
+        global n_finished
+        n_finished += 1
+
+if __name__ == '__main__':
+    for i in range(n_thread):
+        _thread.start_new_thread(thread_entry, (i,))
+
+    while n_finished < n_thread:
+        pass
+    print("done")