Establish DebConf2018 Facebook page

[積丹尼 Dan Jacobson]

As we know, Facebook's penetration in Taiwan is the highest in the word.
Therefore without a
https://www.facebook.com/DebConf18 , or better yet
https://www.facebook.com/DebConf2018 Facebook page,
(in addition to https://debconf18.debconf.org/ )
well, people (and businesses that we are trying to cooperate with)
just won't think we're for real.