Add Ed25519 signature algorithm

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3585)
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 1324a31..64e5ae6 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -673,6 +673,7 @@
     TLSEXT_SIGALG_ecdsa_secp256r1_sha256,
     TLSEXT_SIGALG_ecdsa_secp384r1_sha384,
     TLSEXT_SIGALG_ecdsa_secp521r1_sha512,
+    TLSEXT_SIGALG_ed25519,
 #endif
 
     TLSEXT_SIGALG_rsa_pss_sha256,
@@ -2136,6 +2137,7 @@
     tls1_check_chain(s, NULL, NULL, NULL, SSL_PKEY_GOST01);
     tls1_check_chain(s, NULL, NULL, NULL, SSL_PKEY_GOST12_256);
     tls1_check_chain(s, NULL, NULL, NULL, SSL_PKEY_GOST12_512);
+    tls1_check_chain(s, NULL, NULL, NULL, SSL_PKEY_ED25519);
 }
 
 /* User level utility function to check a chain is suitable */