First draft of template engine chapter

I've added myself to the table of contributors, but I have a few questions about the information we're choosing to present.
Yes please :)

From reading the code and the explanation, I'm not sure why you've chosen to abbreviate `context` to `ctx` or to alias the list `append` and `insert` methods and the `str` built-in.

To my eye, these abbreviations just make the code less readable. Is there something more going on here that I don't understand?