Pretty print Typescript type declarations shipped with xstate

[ethanresnick]

I've been getting started with xstate for the last few days and — despite reading the docs quite thoroughly and understanding the concepts — I often find myself consulting the TS types to discover the exact shape or order of some function's arguments, etc. They are, for those things, the best kind of docs.

Unfortunately, even if one understands the advanced types, the type declarations file is almost impossible to read — just because the lines are so long. So this is a simple request to run prettier or a similar formatter over the generated .d.ts files as part of the package publishing process.