openssl: add subcommand pages (#4886)

pages/common/openssl-req.md

@@ -0,0 +1,12 @@
+# openssl req
+
+> OpenSSL command to manage PKCS#10 Certificate Signing Requests.
+> More information: <https://www.openssl.org/docs/manmaster/man1/openssl-req.html>.
+
+- Generate a certificate signing request to be sent to a certificate authority:
+
+`openssl req -new -sha256 -key {{filename.key}} -out {{filename.csr}}`
+
+- Generate a selfsigned certificate and a corresponding keypair, storing both in a file:
+
+`openssl req -new -x509 -newkey {{rsa}}:{{4096}} -keyout {{filename.key}} -out {{filename.cert}} -subj "{{/C=XX/CN=foobar}}" -days {{365}}`