Adding PWM audio code

Adding PWM audio code for the metro m7 template pages

Metro_M7_Examples/PWM_Tone/code.py

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+# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+
+"""
+CircuitPython PWM Audio Out tone example
+Plays a tone for one second on, one
+second off, in a loop.
+"""
+import time
+import array
+import math
+import board
+from audiocore import RawSample
+from audiopwmio import PWMAudioOut as AudioOut
+
+audio = AudioOut(board.A1)
+
+tone_volume = 0.1  # Increase this to increase the volume of the tone.
+frequency = 440  # Set this to the Hz of the tone you want to generate.
+length = 8000 // frequency
+sine_wave = array.array("H", [0] * length)
+for i in range(length):
+    sine_wave[i] = int((1 + math.sin(math.pi * 2 * i / length)) * tone_volume * (2 ** 15 - 1))
+
+sine_wave_sample = RawSample(sine_wave)
+
+while True:
+    audio.play(sine_wave_sample, loop=True)
+    time.sleep(1)
+    audio.stop()
+    time.sleep(1)

Metro_M7_Examples/PWM_Wav/code.py

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+# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+
+"""
+CircuitPython PWM Audio Out WAV example
+Play a WAV file once.
+"""
+import board
+from audiocore import WaveFile
+from audiopwmio import PWMAudioOut as AudioOut
+
+audio = AudioOut(board.A1)
+
+with open("StreetChicken.wav", "rb") as wave_file:
+    wave = WaveFile(wave_file)
+    print("Playing wav file!")
+    audio.play(wave)
+    while audio.playing:
+        pass
+
+print("Done!")