Adding STEMMA speaker guide files

Author: kattni

Adafruit_STEMMA_Speaker/STEMMA_Speaker_CPX_play_file.py

@@ -0,0 +1,7 @@
+from adafruit_circuitplayground.express import cpx
+
+while True:
+    if cpx.button_a:
+        cpx.play_file("rise.wav")
+    if cpx.button_b:
+        cpx.play_file("dip.wav")

Adafruit_STEMMA_Speaker/STEMMA_Speaker_CPX_play_tone.py

@@ -0,0 +1,7 @@
+from adafruit_circuitplayground.express import cpx
+
+while True:
+    if cpx.button_a:
+        cpx.play_tone(260, 1)
+    if cpx.button_b:
+        cpx.play_tone(292, 1)