Apply DRY to help flag check

The manual check for a `-h | --help` flag is repeated throughout several commands in the project:

```go
if len(os.Args) == 3 && (os.Args[2] == "-h" || os.Args[2] == "--help") {
    flag.Usage()
    return output.String(), nil
}
```

A reusable function will be created in `cmd/utils/`:

```go
if utils.CheckHelpFlag(&output, flag.Usage) {
	return output.String(), nil
}
```