new(userspace/engine): add falco_rule struct to represent rule definitions

Signed-off-by: Jason Dellaluce <jasondellaluce@gmail.com>

userspace/engine/falco_rule.h

@@ -0,0 +1,32 @@
+/*
+Copyright (C) 2022 The Falco Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#pragma once
+
+#include <set>
+#include <string>
+#include "falco_common.h"
+
+struct falco_rule
+{
+	std::string source;
+	std::string name;
+	std::string description;
+	std::string output;
+	std::set<std::string> tags;
+	std::set<std::string> exception_fields;
+	falco_common::priority_type priority;
+};