[TYPES] [newbie contribution] C++ implementations + tests for TAPL

[Kareem Ergawy]

Hello,

Sort of a newbie contribution, hopefully this is interesting for others in
the forum. I am currently self-studying "Types and Programming Languages"
book and decided to provide mature implementations of the languages and
type systems studied in the book in C++. Here is a link to the repo:
https://github.com/KareemErgawy/types-and-programming-languages. Each
implementation contains a large battery of tests and hopefully the code
makes it easy to add new tests.

I am already a full-time software engineer (general C++ development) hoping
to find a compilers-related job in the future and TAPL got me excited to
learn more about type systems.

Hopefully, this is not straying too much from the purpose of the forums and
that folks here are interested in such newbie contributions :).

Best,
Kareem