Add human-readable aliases for different draft versions

[tocic]

Is it possible to add human-readable aliases like https://wg21.link/stdXX?

E.g., https://timsong-cpp.github.io/cppwp/cpp11 for https://timsong-cpp.github.io/cppwp/n3337.

[tocic]

@timsong-cpp What do you think about this? I think it's useful for e.g. SO answers, when you want to reference different versions of the standard and don't want to remember their document numbers.

[timsong-cpp]

Fixed in 220b0cb