feat(parser): add platform-specific parsers and argument conventions

Implement platform-specific parsers for Windows, Linux, and macOS
Add GNU argument convention implementations
Create fake parser for testing purposes
Update CMakeLists to include new headers

include/conventions/base_convention.hpp

@@ -0,0 +1,32 @@
+#pragma once
+#include <string>
+#include <utility>
+
+#ifndef BASE_CONVENTION_HPP
+#define BASE_CONVENTION_HPP
+
+namespace argument_parser::conventions {
+    enum class argument_type {
+        SHORT,
+        LONG,
+        ERROR
+    };
+
+    using parsed_argument = std::pair<argument_type, std::string>; 
+
+    class base_convention {
+        public: 
+        virtual std::string extract_value(std::string const&) const = 0; 
+        virtual parsed_argument get_argument(std::string const&) const = 0;
+        virtual bool requires_next_token() const = 0;
+        virtual std::string name() const = 0; 
+        virtual std::string short_prec() const = 0;
+        virtual std::string long_prec() const = 0;  
+        protected:
+        base_convention() = default;
+        ~base_convention() = default;
+    };
+    using convention = base_convention; 
+}
+
+#endif