New library: argparse, for parsing CLI arguments

[Steven Schveighoffer]

On 10/17/21 6:02 PM, Andrey Zherikov wrote:
> 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.

OMG this looks awesome! I will switch my code to using it...

Prepare for some PRs, I already see ways to make this better ;)

-Steve