add conv for hw2 and complement main.c

hws/hw2/convergence.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include "nr.h"
+#include "nrutil.h"
+
+typedef struct ConvergenceData {
+    int size;
+    float data[200];
+} ConvergenceData;
+
+ConvergenceData rtbis_with_conv(float (*func)(float), float x1, float x2, float xacc);
+ConvergenceData rtflsp_with_conv(float (*func)(float), float x1, float x2, float xacc);
+ConvergenceData rtsec_with_conv(float (*func)(float), float x1, float x2, float xacc);
+ConvergenceData rtnewt_with_conv(void (*funcd)(float, float *, float *), float x1, float x2, float xacc);
+ConvergenceData rtsafe_with_conv(void (*funcd)(float, float *, float *), float x1, float x2, float xacc);
+ConvergenceData rtmuller_with_conv(float (*func)(float), float x1, float x2, float xacc);