renamed header and source file and added dummy header

Author: jaketheduque

src/spo2_algorithm.cpp src/BrainflowSpO2Algorithm.cppsrc/spo2_algorithm.cpp renamed to src/BrainflowSpO2Algorithm.cpp

@@ -4,6 +4,7 @@
 #include <math.h>
 #include <stdlib.h>
 
+#include "EmotiBit_DSPFilters.h"
 #include "DspFilters/Dsp.h"
 
 // These constants are from Table 1 (https://www.analog.com/en/resources/technical-articles/guidelines-for-spo2-measurement--maxim-integrated.html)