[ros-web] Website translation guide

[Zachary Gorden]

Due to Aleksey's nagging, I've put together a translation guide here:
http://www.reactos.org/website-translation

Now that the guide has been effectively formalized, anyone that
manages to break the English site due to not following the
instructions will lose their translation access until they can provide
a written explanation of how to do the translation correctly, in their
own words.