Added renamer exercise

golangr/renamer/go.mod

@@ -0,0 +1,3 @@
+module renamer
+
+go 1.22.0

golangr/renamer/main.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+var src string
+var dst string
+
+func main() {
+	if len(os.Args) != 3 {
+		fmt.Println("Usage: ./renamer oldfile newfile")
+		os.Exit(1)
+	}
+	src = os.Args[1]
+	dst = os.Args[2]
+
+	os.Rename(src, dst)
+
+}