Feature: add custom request header to proxy provider

`header` value is type of string array
header:
  Accept:
    - 'application/vnd.github.v3.raw'
  Authorization:
    - ' token xxxxxxxxxxx'
  User-Agent:
    - 'Clash/v1.10.6'

`prefix-name` add a prefix to proxy name
prefix-name: 'XXX-'

adapter/provider/vehicle.go

@@ -9,7 +9,9 @@ import (
 	"os"
 	"time"
 
+	"github.com/Dreamacro/clash/common/convert"
 	"github.com/Dreamacro/clash/component/dialer"
+	C "github.com/Dreamacro/clash/constant"
 	types "github.com/Dreamacro/clash/constant/provider"
 )
 
@@ -34,8 +36,9 @@ func NewFileVehicle(path string) *FileVehicle {
 }
 
 type HTTPVehicle struct {
-	url  string
-	path string
+	url    string
+	path   string
+	header http.Header
 }
 
 func (h *HTTPVehicle) Type() types.VehicleType {
@@ -60,11 +63,19 @@ func (h *HTTPVehicle) Read() ([]byte, error) {
 		return nil, err
 	}
 
+	if h.header != nil {
+		req.Header = h.header
+	}
+
 	if user := uri.User; user != nil {
 		password, _ := user.Password()
 		req.SetBasicAuth(user.Username(), password)
 	}
 
+	if req.UserAgent() == "" {
+		convert.SetUserAgent(req)
+	}
+
 	req = req.WithContext(ctx)
 
 	transport := &http.Transport{
@@ -73,8 +84,13 @@ func (h *HTTPVehicle) Read() ([]byte, error) {
 		IdleConnTimeout:       90 * time.Second,
 		TLSHandshakeTimeout:   10 * time.Second,
 		ExpectContinueTimeout: 1 * time.Second,
-		DialContext: func(ctx context.Context, network, address string) (net.Conn, error) {
-			return dialer.DialContext(ctx, network, address)
+		DialContext: func(ctx context.Context, network, address string) (conn net.Conn, err error) {
+			conn, err = dialer.DialContext(ctx, network, address) // with direct
+			if err != nil {
+				// fallback to tun if tun enabled
+				conn, err = (&net.Dialer{Timeout: C.DefaultTCPTimeout}).Dial(network, address)
+			}
+			return
 		},
 	}
 
@@ -83,7 +99,9 @@ func (h *HTTPVehicle) Read() ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer resp.Body.Close()
+	defer func() {
+		_ = resp.Body.Close()
+	}()
 
 	buf, err := io.ReadAll(resp.Body)
 	if err != nil {
@@ -93,6 +111,6 @@ func (h *HTTPVehicle) Read() ([]byte, error) {
 	return buf, nil
 }
 
-func NewHTTPVehicle(url string, path string) *HTTPVehicle {
-	return &HTTPVehicle{url, path}
+func NewHTTPVehicle(url string, path string, header http.Header) *HTTPVehicle {
+	return &HTTPVehicle{url, path, header}
 }