Move shared rule pointer factories into individual rule files

src/rules/rule.h

@@ -15,7 +15,16 @@ namespace tree_sitter {
         };
         
         typedef std::shared_ptr<const Rule> rule_ptr;
+
         std::ostream& operator<<(std::ostream& stream, const Rule &rule);
+
+        template <typename RuleClass>
+        rule_ptr build_binary_rule_tree(const std::initializer_list<rule_ptr> &rules) {
+            rule_ptr result(nullptr);
+            for (auto it = rules.end() - 1; it >= rules.begin(); --it)
+                result = result.get() ? std::make_shared<RuleClass>(*it, result) : *it;
+            return result;
+        }
     }
 }