Support slice with ParseEnv

[artemklevtsov]

System (please complete the following information):

• OS: linux
• GO Version: 1.19.4
• Pkg Version: 2.1.8

Describe the bug

Slice not parser with environment variables.

To Reproduce

package main

import (
	"github.com/gookit/config/v2"
)

var version = "dev"

type conf struct {
	Name  string   `mapstructure:"name" default:"${NAME | Bob}"`
	Value []string `mapstructure:"value" default:"${VAL | val1}"`
}

func main() {

	config.WithOptions(
		config.ParseDefault,
		config.ParseEnv,
		config.Readonly,
	)

	err := config.LoadExists("")
	if err != nil {
		panic(err)
	}

	var cc conf
	if err := config.Decode(&cc); err != nil {
		panic(err)
	}
}

Actual behavior

panic: convert value type error

goroutine 1 [running]:
main.main()
        /run/media/unikum/UNIKUM-STORAGE/work/centrofinans/dev/kafka-tb-translator/tools/conf/main.go:29 +0xd1
exit status 2

[inhere]

Added and released on https://github.com/gookit/config/releases/tag/v2.2.0