Document that transliteration is in D8 core

#567832: Transliteration in core (Change notice: Transliteration class added)... Yay!

This should be in the project's front page and perhaps we should be looking into figuring ways to best take advantage of this. Related issue + a place to suggest ideas of how to take advantage of the fresh feature: #1842718: Use new Transliteration functionality in core for machine names

So, can you please list these links somewhere in the front page + perhaps in the documentation section? An example of how to use hook_transliteration_overrides_alter() would be great too. Thanx ;)

PS: I know I might be rushing (there's no 8.x branch yet), but this is exciting news.