spell out that Matrix is more concerned with bridging than XMPP

supporting-docs/guides/2015-08-19-faq.md

@@ -226,6 +226,8 @@ drove us in this direction were:
     FMUC improves this with a similar approach to Matrix, but as of Oct
     2015 there are no open source implementations.)
 -   History synchronisation is very much a second class citizen feature
+-   Bridging to other protocols and defragmenting existing communication
+    apps and networks is very much a second class citizen feature
 -   Stanzas aren't framed or reliably delivered without extensions. (See
     [wiki.xmpp.org](http://wiki.xmpp.org/web/Myths#Myth_Four:_XMPP_is_unreliable_without_a_bunch_of_extensions.)
     for an XMPP take on this)