Add sample programs

[tsani]

The language overview as it is doesn't actually explain anything beyond the core syntax, without even using the real symbols for the constructs. Since we've more or less settled on what symbols we'll be using, we should use the real symbols, and begin writing real usage guides / documentation.

[tsani]

Changed title because there's a separate issue about docs. This should just concern sample programs, so that people can get a look at what the language looks like.

[gumgl]

I thought I had used the right symbols but I might have made some errors trying to keep the grammar (Unicode code points) and the UI (emoji shortnames) in sync. I did change some symbols in the grammar that were not supported by emojione.com though. Just realized you were not talking about the "constructs" tree of the IDE but about the language overview in the README, disregard this message! in fact, this comment should have been in #8