Add basic clash api

option/experimental.go

@@ -0,0 +1,10 @@
+package option
+
+type ExperimentalOptions struct {
+	ClashAPI *ClashAPIOptions `json:"clash_api,omitempty"`
+}
+
+type ClashAPIOptions struct {
+	ExternalController string `json:"external_controller,omitempty"`
+	Secret             string `json:"secret,omitempty"`
+}