Add Mewa compiler-compiler to the list

* [Mewa](https://github.com/patrickfrey/mewa) - Writing compiler front-ends of statically-typed languages for LLVM with Lua.

Mewa is a compiler-compiler for prototyping compiler front-ends for statically typed languages using LLVM IR as back-end in Lua.
The main emphasis of the project is not on the parser generator but on the support for defining a type system.
It aims to bring projects considered endless for a single person within reach ( ~ 5K Lines of Code ).
An example implementation of a non-trivial compiler and an FAQ exists to help you in problem-solving.