Initial documentation for the Monero libraries (#122)

* Document all features

* Largely document the Monero libraries

Relevant to https://github.com/serai-dex/serai/issues/103 and likely 
sufficient to get this removed from 
https://github.com/serai-dex/serai/issues/102.

coins/monero/src/tests/clsag.rs

@@ -120,8 +120,7 @@ fn clsag_multisig() -> Result<(), MultisigError> {
           .unwrap(),
           mask_sum,
         )))),
-      )
-      .unwrap(),
+      ),
       &keys,
     ),
     &[1; 32],