Mir Ion and Asdf benchmakrs

[9il]

mir-ion and Asdf JSON libraries have been added to the 
Kostya/benchmarks.

https://github.com/kostya/benchmarks#json

If we exclude parsers with inaccurate number parsing then the top 
will be

1. C++, simdjson
2. Rust, Serde
3. Dlang, Mir Amazon's Ion DOM
4. Dlang, Mir Asdf DOM
5. C++ RapidJSON (Precise)

Mir Ion has been inspired by simdjson and Amazon's Ion binary 
format, which is used as DOM. Thus the mir-ion DOM for the 112 
MiB file costs 16 MiB comparing with 176 MiB DOM in simdjson.

Kind regards,
Ilya