Chapter 13 Inheritance

* I apparently forgot to commit the LoxClass to the class chapter,
so I `--amend`ed the previous commit, but then it tracks this chapter.
I don't care too much about that, but now it's out of order :)
Chapter 12 Classes
Chapter 11 Resolving and Binding
Chapter 10 Functions
Chapter 9

* Answers the first two challenges
* Attempted and then looked up the answer for the third challenge
Adding repo

Chapters up to 9 were completed already for Jlox.