New library: argparse, for parsing CLI arguments

[Andrey Zherikov]

On Thursday, 14 October 2021 at 15:03:34 UTC, Steven 
Schveighoffer wrote:
> Having done a lot of stuff with serialization and UDAs, this 
> turns into a mess if you have multiple systems (serialization 
> is really what you are doing here) using the same structs. So 
> really, you are likely to have this `Params` struct be 
> distinctly for parameter parsing. It's OK to have requirements 
> such as expecting all items to be serialized by default and in 
> a default way.

Structs without UDA are now supported starting version `0.4.0`. I 
also added this use case as a basic into "Getting started" 
section in readme.