🚀 [Feature]: filesystem.Config add file encoding property support

[baichangda]

Feature Description

now use filesystem like this、the response header content-type of the file has no charset、hope add property in filesystem.Config for response header content-type charset

Additional Context (optional)

No response

Code Snippet (optional)

package main

import "github.com/gofiber/fiber/v2"
import "github.com/gofiber/fiber/v2/middleware/filesystem"
import "log"
//go:embed resource/*
var FS embed.FS
func main() {
app.Use("/", filesystem.New(filesystem.Config{
		Root:       http.FS(FS),
		PathPrefix: "resource",
		Browse:     true,
                 ContentTypeCharset: "utf-8",
	}))
}

Checklist:

• I agree to follow Fiber's Code of Conduct.
• I have checked for existing issues that describe my suggestion prior to opening this one.
• I understand that improperly formatted feature requests may be closed without explanation.

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