doc: add manpage entry for --use-system-ca

PR-URL: https://github.com/nodejs/node/pull/59273
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ulises Gascón <ulisesgascongonzalez@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Harshitha K P <harshitha014@gmail.com>

doc/node.1

@@ -613,6 +613,13 @@ See
 and
 .Ev SSL_CERT_FILE .
 .
+.It Fl -use-system-ca
+Use the trusted CA certificates present in the system store, in addition to the certificates in the
+bundled Mozilla CA store and certificates from `NODE_EXTRA_CA_CERTS`. On Windows and macOS, it uses system APIs to
+integrate additional trusted certificates. On other platforms it is similar to `--use-openssl-ca` with the difference
+being that it caches the certificates on first load, and the system certificates are added in a complementary manner
+without replacing certificates from other sources. This flag supersedes `--use-openssl-ca`.
+.
 .It Fl -use-largepages Ns = Ns Ar mode
 Re-map the Node.js static code to large memory pages at startup. If supported on
 the target system, this will cause the Node.js static code to be moved onto 2