Provide documentation for the -psk_session option

The s_client/s_server docs were missing documentation for this option.
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6215)

doc/man1/s_client.pod

@@ -71,6 +71,9 @@ B<openssl> B<s_client>
 [B<-crlf>]
 [B<-ign_eof>]
 [B<-no_ign_eof>]
+[B<-psk_identity identity>]
+[B<-psk key>]
+[B<-psk_session file>]
 [B<-quiet>]
 [B<-ssl3>]
 [B<-tls1>]
@@ -409,6 +412,11 @@ given as a hexadecimal number without leading 0x, for example -psk
 1a2b3c4d.
 This option must be provided in order to use a PSK cipher.
 
+=item B<-psk_session file>
+
+Use the pem encoded SSL_SESSION data stored in B<file> as the basis of a PSK.
+Note that this will only work if TLSv1.3 is negotiated.
+
 =item B<-ssl3>, B<-tls1>, B<-tls1_1>, B<-tls1_2>, B<-tls1_3>, B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3>
 
 These options require or disable the use of the specified SSL or TLS protocols.

doc/man1/s_server.pod

@@ -157,6 +157,7 @@ B<openssl> B<s_server>
 [B<-psk_identity val>]
 [B<-psk_hint val>]
 [B<-psk val>]
+[B<-psk_session file>]
 [B<-srpvfile infile>]
 [B<-srpuserseed val>]
 [B<-ssl3>]
@@ -597,6 +598,11 @@ given as a hexadecimal number without leading 0x, for example -psk
 1a2b3c4d.
 This option must be provided in order to use a PSK cipher.
 
+=item B<-psk_session file>
+
+Use the pem encoded SSL_SESSION data stored in B<file> as the basis of a PSK.
+Note that this will only work if TLSv1.3 is negotiated.
+
 =item B<-listen>
 
 This option can only be used in conjunction with one of the DTLS options above.