Added missing SPDX info

Author: TrevKnows

Matrix_Portal_M4_Boxing_Interval_Timer/code.py

@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: 2023 Trevor Beaton for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+
 import time
 import displayio
 import terminalio