Ubuntu required dependencies for Swift

[IanPartridge]

@tkremenek posted recently about opening up the website to contributions so hopefully we'll be able to fix things like this soon!

RFC: making Swift.org a more valuable resource for the Swift community

The Swift.org website is meant to serve two purposes: Be the home page of the Swift language and the Swift community, and serving the general population of Swift users. Be a nexus for Swift as an open source project (i.e., the implementation of Swift itself), which spans multiple repositories on GitHub. While there is some good material on the Swift.org website, what is currently there underserves both of the two goals mentioned above and there is a lot more that can be done. We are pr…