Do you accept contributions?

[notramo]

@grkek I took a look into the source code, and it seems it is using older approaches, or solutions that were necessary with an older version of the standard library.
I want to contribute some improvements, but I only open PR if I know that it will get attention.

For example, Grip::Parsers::ParameterBox::AllParamsType is unnecessary as it's the same as the JSON::Any::Type in the latest version of the standard library.

Also, the standard library includes a HTTP::Request#query_params in the latest version.

There are some places in the documentation that could be improved also.

[Giorgi Kavrelishvili]

I pay attention to PR's ASAP, make a PR for the above-mentioned problems and I would be more than happy to take a look at them.