refactor(argument_parser): improve argument handling and cleanup code

- Add new template method for argument addition with type
- Handle optional values more safely in get_optional
- Remove commented test code from main.cpp

src/main.cpp

@@ -105,10 +105,9 @@ auto make_grep_action(argument_parser::base_parser& parser) {
 }
 
 int main() {
-    // std::vector<std::string> fake_args = { "-g", "add", "-f", "src/main.cpp", "-ep", "1,2" };
-    // auto parser = argument_parser::fake_parser{"test", std::move(fake_args)};
     auto parser = argument_parser::parser{};
     auto [file, grep] = make_grep_action(parser); 
+    
     parser.add_argument("e", "echo", "echoes given variable", echo, false);
     parser.add_argument("ep", "echo-point", "echoes given point", echo_point, false);
     parser.add_argument("f", "file", "File to grep, required only if using grep", file, false);