Add an IndexByte implementation useful for benchmarking against stdlib SIMD implementation

tools/simdstring/scalar.go

@@ -2,6 +2,24 @@
 
 package simdstring
 
+func index_byte_scalar(data []byte, b byte) int {
+	for i, ch := range data {
+		if ch == b {
+			return i
+		}
+	}
+	return -1
+}
+
+func index_byte_string_scalar(data string, b byte) int {
+	for i := 0; i < len(data); i++ {
+		if data[i] == b {
+			return i
+		}
+	}
+	return -1
+}
+
 func index_byte2_scalar(data []byte, a, b byte) int {
 	for i, ch := range data {
 		switch ch {