[ANN] Natural constants: a crate containing just numbers

[willi_kappler]

Hi Rustaceans,

I'm happy to announce a new crate: natural_constants.
The goal is to collect all the numbers you care about and provide a nice and easy to use interface for them.

There's still a lot of work to do, so if your favorite constant is missing just let us know.

[zen3ger]

I know it's not really something but it would be awesome to have a meaning_of_life somewhere.

[willi_kappler]

Yes, will add that number