Change `richtr.github.com` to `richtr.github.io` at link demo README.md

[LiuQBinh]

At this line, can you correct the link to https://richtr.github.io/guessLanguage.js/?

Because at current time, it is a 404 page.
https://github.com/richtr/guessLanguage.js/blob/master/README.md?plain=1#L8