crypto/x509: add Ed25519 to ExampleParsePKIXPublicKey

ParsePKIXPublicKey gained Ed25519 support in CL 175478.

Change-Id: I11ffe0a62743292367b3adb103956e61bad57cc4
Reviewed-on: https://go-review.googlesource.com/c/go/+/183243Reviewed-by: Katie Hockman <katie@golang.org>

src/crypto/x509/example_test.go

@@ -7,6 +7,7 @@ package x509_test
 import (
 	"crypto/dsa"
 	"crypto/ecdsa"
+	"crypto/ed25519"
 	"crypto/rsa"
 	"crypto/x509"
 	"encoding/pem"
@@ -128,6 +129,8 @@ AIU+2GKjyT3iMuzZxxFxPFMCAwEAAQ==
 		fmt.Println("pub is of type DSA:", pub)
 	case *ecdsa.PublicKey:
 		fmt.Println("pub is of type ECDSA:", pub)
+	case ed25519.PublicKey:
+		fmt.Println("pub is of type Ed25519:", pub)
 	default:
 		panic("unknown type of public key")
 	}