Add SPDX license to Arduino specimens

Author: PaintYourDragon

EyeLights_Accelerometer_Tap/EyeLights_Accelerometer_Tap.ino

@@ -1,3 +1,7 @@
+// SPDX-FileCopyrightText: 2021 Phil Burgess for Adafruit Industries
+//
+// SPDX-License-Identifier: MIT
+
 /*
 ACCELEROMETER INPUT DEMO: while the LED Glasses Driver has a perfectly
 good clicky button for input, this code shows how one might instead use

EyeLights_Audio_Spectrum/EyeLights_Audio_Spectrum.ino

@@ -1,3 +1,7 @@
+// SPDX-FileCopyrightText: 2021 Phil Burgess for Adafruit Industries
+//
+// SPDX-License-Identifier: MIT
+
 /*
 AUDIO SPECTRUM LIGHT SHOW for Adafruit EyeLights (LED Glasses + Driver).
 Uses onboard microphone and a lot of math to react to music.

EyeLights_Googly_Rings/EyeLights_Googly_Rings.ino

@@ -1,3 +1,7 @@
+// SPDX-FileCopyrightText: 2021 Phil Burgess for Adafruit Industries
+//
+// SPDX-License-Identifier: MIT
+
 /*
 GOOGLY EYES for Adafruit EyeLight LED glasses + driver. Pendulum physics
 simulation using accelerometer and math. This uses only the rings, not the