cfssl: add page (#14378)

* cfssl: add page

---------

Co-authored-by: Wiktor Perskawiec <git@spageektti.cc>

pages/common/cfssl.md

@@ -0,0 +1,21 @@
+# cfssl
+
+> Cloudflare's PKI and TLS toolkit.
+> See also: `openssl`.
+> More information: <https://github.com/cloudflare/cfssl>.
+
+- Show certificate information of a host:
+
+`cfssl certinfo -domain {{www.google.com}}`
+
+- Decode certificate information from a file:
+
+`cfssl certinfo -cert {{path/to/certificate.pem}}`
+
+- Scan host(s) for SSL/TLS issues:
+
+`cfssl scan {{host1 host2 ...}}`
+
+- Display help for a subcommand:
+
+`cfssl {{genkey|gencsr|certinfo|sign|gencrl|ocspdump|ocsprefresh|ocspsign|ocspserve|scan|bundle|crl|print-defaults|revoke|gencert|serve|version|selfsign|info}} -h`