Executable listings

When it comes to engine-specific editions (Like the planned SFML edition, see #122) it would be nice to add executable listings of code.

Each language package would get bundled with a bunch of well-commented source code listings that can be compiled (if necessary) by the reader, as well as modified (by having separated variables that they can change, for instance to change the behaviour of a jump).

Eventually the engine-aware editions can refer to those executables via specific boxes.

Look at the repository structure to understand how language packages are organized. Examine existing code listings and documentation boxes. The task involves creating executable, well-commented source code listings for each language package (like Rust, Python, C++, JavaScript) that can be compiled and modified. Check for references to engine-specific editions and how they might link to these new listings. Verify the integration points for the 'engine-aware editions' to refer to these executables via specific boxes.

索引モデルが issue の本文から書いたものです。