added arduino, modified build

arduino/libraries/Adafruit_Circuit_Playground/examples/Microphone_Demos/soundPressureLevel/soundPressureLevel.ino

@@ -0,0 +1,18 @@
+/* This example samples the microphone for 50 milliseconds repeatedly
+ * and returns the max sound pressure level in dB SPL
+ * https://en.wikipedia.org/wiki/Sound_pressure
+ *
+ * open the serial plotter window in the arduino IDE for a nice graph
+ * of sound pressure level over time.
+ */
+
+#include <Adafruit_CircuitPlayground.h>
+
+void setup() {
+  CircuitPlayground.begin();
+  Serial.begin(115200);
+}
+
+void loop() {
+  Serial.println(CircuitPlayground.mic.soundPressureLevel(50));
+}