Add Ed25519 to signature algorithm table

Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3585)

ssl/t1_lib.c

@@ -717,6 +717,9 @@ static const SIGALG_LOOKUP sigalg_lookup_tbl[] = {
     {"ecdsa_secp521r1_sha512", TLSEXT_SIGALG_ecdsa_secp521r1_sha512,
      NID_sha512, SSL_MD_SHA512_IDX, EVP_PKEY_EC, SSL_PKEY_ECC,
      NID_ecdsa_with_SHA512, NID_secp521r1},
+    {"ed25519", TLSEXT_SIGALG_ed25519,
+     NID_undef, -1, NID_ED25519, SSL_PKEY_ED25519,
+     NID_undef, NID_undef},
     {NULL, TLSEXT_SIGALG_ecdsa_sha224,
      NID_sha224, SSL_MD_SHA224_IDX, EVP_PKEY_EC, SSL_PKEY_ECC,
      NID_ecdsa_with_SHA224, NID_undef},