update: builder pattern with typestate example

[dzmitry-lahoda]

problem

current https://rust-unofficial.github.io/patterns/patterns/creational/builder.html?highlight=builder#builder is not typestate based, so it actually does nothing useful

solution

show how to manually do https://github.com/elastio/bon, and then how it will be done just using bon

note

also bon does idiomatic partial application in rust, not sure - may be it should go as separate pattern