Parse and pretty print the type inference marker _.
Parse _n.
Add missing pattern matching cases for type inference AST node.

Not so sure about the eval function in
`src-lib/PTS/Dynamics/Evaluation.hs:127:14`. There is no reasonable evaluation
of `_` but can this case even occur? If it cannot, what is the best way to
handle non-exhaustive patterns that will actually be exhaustive at runtime?
Fix typo.
Add missing cases to eval.
Merge branch 'parse_' into bidi
Fix build.

I need a pre-commit hook that cleans and rebuilds the project. Apparently I keep
forgetting to actually build everything after changing stuff.
Examples and tests for type inference.
First working instance of type inference. In heavy need of refactoring.