Add benchmark

bench/fibonacci.c

@@ -0,0 +1,20 @@
+int fibonacci_loop(int n, int nonce) {
+  int x = nonce;
+  int y = nonce;
+
+  for (int i = 1; i < n; ++i) {
+    int newy = x + y;
+    x = y;
+    y = newy;
+  }
+
+  return y;
+}
+
+int fibonacci_recursive(int n, int nonce) {
+  if (n < 2) {
+    return nonce;
+  }
+
+  return fibonacci_recursive(n - 1, nonce) + fibonacci_recursive(n - 2, nonce);
+}