Add helper functions for making shared pointers to rules

- start work on item set class

src/rules/Pattern.cpp

@@ -0,0 +1,21 @@
+#include "Pattern.h"
+#include "transition_map.h"
+
+namespace tree_sitter {
+    namespace rules {
+        Pattern::Pattern(const std::string &string) : value(string) {};
+        Pattern::Pattern(const char *string) : value(string) {};
+
+        TransitionMap<Rule> Pattern::transitions() const {
+            return tree_sitter::TransitionMap<Rule>();
+        }
+
+        bool Pattern::operator ==(tree_sitter::rules::Rule const &other) const {
+            return false;
+        }
+
+        std::string Pattern::to_string() const {
+            return value;
+        }
+    }
+}