`deno_ast` Might Simplify TypeScript Compilation

[zicklag]

The deno_ast crate might simplify the TypeScript transpiler code a little.

https://github.com/denoland/deno/blob/2703996dea73c496d79fcedf165886a1659622d1/core/examples/ts_module_loader.rs#L68-L78

Unless you need to customize the process. I couldn't tell yet if you were doing anything that needed more control over the process that deno_ast provides.

[jakobhellermann]

Done in ae334f5