Add additional Cylinder JWT info to manpage
This change adds a short description of Cylinder JWT to the splinterd
manpage.  It provides some context for the previous paragraphs that
reference it, but don't describe it.
@@ -324,6 +324,12 @@ Cylinder JWT, and OAuth.
Cylinder JWT authorization is enabled by default.
+A Cylinder JWT is a custom JSON Web Token implementation which supports the
+signing algorithms provided by the Cylinder library. This includes secp256k1
+which is currently used for signing transactions and Splinter administrative
+payloads. This allows the same signing key to be used as an authorization
+identity.
+
Biome credentials for the splinter REST API can be enabled using the
`--enable-biome` flag.
