feat: rfc1 external_spec commands

swift-secure-enclave-tool-v2.swift

@@ -251,6 +251,7 @@ struct ExternalSpecResponse: Codable {
     var success: Bool
     var agent: String
     var specification: String
+    var commands: Array<String>
 }
 
 func stringify<T: Encodable>(_ value: T) -> String? {
@@ -460,7 +461,8 @@ func externalSpec() -> ExternalSpecResponse {
     return ExternalSpecResponse(
         success: true,
         agent: "swift-secure-enclave-external-provider/2.0.0-alpha",
-        specification: "External/1.0.0-alpha"
+        specification: "External/1.0.0-alpha",
+        commands: ["external_public_key", "external_sign"]
     )
 }