Add quine example (self-replicating code)

[woodrush]

A quine is a program that outputs its own source code. When you input ./examples/quine.wy in the interpreter, it prints exactly the same string as its original source code.

This commit adds a quine program that I've written in wenyan-lang.

The original idea of the implementation, that quines in JavaScript can be implemented via replacement of strings, is referenced from a code in this post by @amo12937 . I've mentioned the URL of this post inside the source code.

[woodrush]

One large room of improvement that can be made on this code is that it explicitly states String.fromCharCode inside the source code. This problem can be fixed straightforwardly by implementing #84 .

[woodrush]

... it prints exactly the same string as its original source code.

Just for clarity, the code doesn't output the comment at the top.

[LingDong-]

Wow!! Thanks so much! I always wanted a quine example, but how to make one was beyond me ;)

[woodrush]

Thanks for the merge! You're welcome! ;) It was fun writing it in this language. I especially like the rendering of the script, thanks for the cool project!