context: Add program directory's path

includes/context.hpp

@@ -33,6 +33,7 @@ typedef struct ctx {
   std::shared_ptr<Selection> selection = nullptr;
   std::shared_ptr<PaternsMenu> paterns_menu = nullptr;
   nlohmann::json config_json;
+  std::filesystem::path program_dir;
 } ctx;
 
 } // namespace gol