update: README.md

Author: 54m

README.md

@@ -1 +1,31 @@
-# chunk
+# What is this?
+Obtains an index of specified size length and returns it.  
+
+# Usage
+
+```go
+package main
+
+import (
+	"fmt"
+
+	"github.com/go-utils/chunk"
+)
+
+func main() {
+	arr := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
+
+	chunkedArr := make([][]int, 0)
+	// chunk size is 3
+	for idx := range chunk.GetIndex(len(arr), 3) {
+		chunkedArr = append(chunkedArr, arr[idx.From:idx.To])
+	}
+
+	fmt.Printf("%#v\n", chunkedArr)
+	// Output: [][]int{[]int{1, 2, 3}, []int{4, 5, 6}, []int{7, 8, 9}, []int{10}}
+}
+```
+
+## License
+- Under the [MIT License](./LICENSE)
+- Copyright (C) 2022 go-utils