Add rule precedence construct

Still need to add some way of expressing left and right
associativity

src/compiler/util/string_helpers.h

@@ -2,11 +2,17 @@
 #define COMPILER_UTIL_STRING_HELPERS_H_
 
 #include <string>
+#include <vector>
+#include <set>
 
 namespace tree_sitter {
     namespace util {
         void str_replace(std::string *input, const std::string &search, const std::string &replace);
         std::string escape_string(std::string input);
+        std::string indent(std::string input);
+        std::string join(std::vector<std::string> lines, std::string separator);
+        std::string join(std::vector<std::string> lines);
+        std::string character_code(char character);
     }
 }