Fix missing copyright on example json service

Author: mraleson

examples/ble_json_service.py

@@ -1,3 +1,9 @@
+# SPDX-FileCopyrightText: 2020 Mark Raleson
+#
+# SPDX-License-Identifier: MIT
+
+# Read sensor readings from peripheral BLE device using a JSON characteristic.
+
 from adafruit_ble.uuid import VendorUUID
 from adafruit_ble.services import Service
 from adafruit_ble.characteristics import Characteristic