add js stub impl

netroute_stub.go

+// A stub routing table conformant interface for js/wasm environments.
+
+// +build js,wasm
+
+package netroute
+
+import (
+	"net"
+
+	"github.com/google/gopacket/routing"
+)
+
+func New() (routing.Router, error) {
+	rtr := &router{}
+	rtr.ifaces = make(map[int]net.Interface)
+	rtr.ifaces[0] = net.Interface{}
+	rtr.addrs = make(map[int]ipAddrs)
+	rtr.addrs[0] = ipAddrs{}
+	rtr.v4 = routeSlice{&rtInfo{}}
+	rtr.v6 = routeSlice{&rtInfo{}}
+	return rtr, nil
+}