Support for bad commas

[nuzrub]

• Some of the projects I work on use man-made Jsons as config files. At start it is nice, then people start to forget some commas at the end of objects/arrays. When using Newtonsoft's Json.Net, it handles it gracefully, just ignoring. When using yours, it gives me an error. Thus, I have to correct some files from time to time so that they can be read.
  I love your lib and that feature would make my life easier.

• A minimal Json with bad commas:

{
    "A": 10,
}
           /\ Bad Comma

As I see it, the comma puts the lib in a state where it expects some other member, but it gets a } instead. Thus, the grammar must be slightly altered to allow , } as just being a }. Same goes for ,] being threated as just a ]

Thanks for the Lib :)

[OvermindDL1]

Wouldn't that be breaking the JSON spec though? I'm pretty sure there are tests where that is specifically and explicitly supposed to fail and those conformance tests would no longer pass then?

[nuzrub]

Maybe there could be a library wide switch or #define toggling this behavior.

[nlohmann]

This is a duplicate of #376. This library will not support inputs that are not conforming to RFC 8259.