Add listwallets method

Author: fanquake

Sources/CoreRPC/Methods.swift

@@ -36,6 +36,7 @@ public enum RPCMethod: String, Codable {
     case help = "help"
     case listbanned = "listbanned"
     case listunspent = "listunspent"
+    case listwallets = "listwallets"
     case loadwallet = "loadwallet"
     case logging = "logging"
     case sendrawtransaction = "sendrawtransaction"

Sources/CoreRPC/Wallet.swift

@@ -15,6 +15,10 @@ public extension CoreRPC {
         return call(method: .listunspent, params: Empty())
     }
 
+    func listWallets() -> Promise<[String]> {
+        return call(method: .listwallets, params: Empty())
+    }
+
     struct LoadedWallet: Decodable {
         let name: String
         let warning: String