dillon1000/react

[rust] Fixture tests for parsing and lowering

Adds a new `fixtures` crate intended for running end-to-end tests of the 
compiler. As we expand the compiler this will eventually match our JS fixture 
setup, where we have .js files as input and produce memoized JS output. 

For now, this does the following: 

* Parses with SWC (omg this was painful to setup) 

* Runs SWC's name resolution, which annotates the SWC ast in-place 

* Convert the SWC ast into our `estree` representation 

* Convert `estree` into `hir` for each top-level function declaration in the 
input program 

* Print the Rust `Debug` view of the resulting HIR 

As a next step i'll add a pretty-printer for the HIR to roughly match what we 
have in JS.