Support Restls-V1 in Clash.Meta (#441)

* feat: impl restls

* fix: don't break shadowtls' working

* chores: correct restls-client-go version

* feat: bump restls-client-go version

* fix: consistent naming `client-fingerprint`

* docs: update example config

* chore: adjust client-fingerprint's snippet

---------

Co-authored-by: wwqgtxx <wwqgtxx@gmail.com>
Co-authored-by: Larvan2 <78135608+Larvan2@users.noreply.github.com>

transport/restls/restls.go

@@ -0,0 +1,57 @@
+package restls
+
+import (
+	"net"
+
+	tls "github.com/3andne/restls-client-go"
+)
+
+const (
+	Mode string = "restls"
+)
+
+// Restls
+type Restls struct {
+	net.Conn
+	firstPacketCache []byte
+	firstPacket      bool
+}
+
+func (r *Restls) Read(b []byte) (int, error) {
+	if err := r.Conn.(*tls.UConn).Handshake(); err != nil {
+		return 0, err
+	}
+	n, err := r.Conn.(*tls.UConn).Read(b)
+	return n, err
+}
+
+func (r *Restls) Write(b []byte) (int, error) {
+	if r.firstPacket {
+		r.firstPacketCache = append([]byte(nil), b...)
+		r.firstPacket = false
+		return len(b), nil
+	}
+	if len(r.firstPacketCache) != 0 {
+		b = append(r.firstPacketCache, b...)
+		r.firstPacketCache = nil
+	}
+	n, err := r.Conn.(*tls.UConn).Write(b)
+	return n, err
+}
+
+// NewRestls return a Restls Connection
+func NewRestls(conn net.Conn, config *tls.Config) (net.Conn, error) {
+	if config != nil {
+		clientIDPtr := config.ClientID.Load()
+		if clientIDPtr != nil {
+			return &Restls{
+				Conn:        tls.UClient(conn, config, *clientIDPtr),
+				firstPacket: true,
+			}, nil
+		}
+	}
+	return &Restls{
+		Conn:        tls.UClient(conn, config, tls.HelloChrome_Auto),
+		firstPacket: true,
+	}, nil
+}