add vendoring

vendor/github.com/mikesmitty/edkey/README.md

@@ -0,0 +1,32 @@
+# edkey
+edkey allows you to marshal/write ED25519 private keys in the OpenSSH private key format
+
+## Example
+```go
+package main
+
+import (
+	"crypto/rand"
+	"encoding/pem"
+	"io/ioutil"
+	"github.com/mikesmitty/edkey"
+	"golang.org/x/crypto/ed25519"
+	"golang.org/x/crypto/ssh"
+)
+
+func main() {
+	// Generate a new private/public keypair for OpenSSH
+	pubKey, privKey, _ := ed25519.GenerateKey(rand.Reader)
+	publicKey, _ := ssh.NewPublicKey(pubKey)
+
+	pemKey := &pem.Block{
+		Type:  "OPENSSH PRIVATE KEY",
+		Bytes: edkey.MarshalED25519PrivateKey(privKey),
+	}
+	privateKey := pem.EncodeToMemory(pemKey)
+	authorizedKey := ssh.MarshalAuthorizedKey(publicKey)
+
+	_ = ioutil.WriteFile("id_ed25519", privateKey, 0600)
+	_ = ioutil.WriteFile("id_ed25519.pub", authorizedKey, 0644)
+}
+```