Support resampling (#77)

sherpa-onnx/csrc/features.h

@@ -29,9 +29,11 @@ class FeatureExtractor {
   ~FeatureExtractor();
 
   /**
-     @param sampling_rate The sampling_rate of the input waveform. Should match
-                          the one expected by the feature extractor.
-     @param waveform Pointer to a 1-D array of size n
+     @param sampling_rate The sampling_rate of the input waveform. If it does
+                          not equal to  config.sampling_rate, we will do
+                          resampling inside.
+     @param waveform Pointer to a 1-D array of size n. It must be normalized to
+                     the range [-1, 1].
      @param n Number of entries in waveform
    */
   void AcceptWaveform(int32_t sampling_rate, const float *waveform, int32_t n);