fix(settings): VPNSP value read as lowercase

internal/configuration/sources/env/vpn.go

@@ -3,12 +3,13 @@ package env
 import (
 	"fmt"
 	"os"
+	"strings"
 
 	"github.com/qdm12/gluetun/internal/configuration/settings"
 )
 
 func (r *Reader) readVPN() (vpn settings.VPN, err error) {
-	vpn.Type = os.Getenv("VPN_TYPE")
+	vpn.Type = strings.ToLower(os.Getenv("VPN_TYPE"))
 
 	vpn.Provider, err = r.readProvider(vpn.Type)
 	if err != nil {