Fix keyword argument passing in Ruby 3

[lulalala]

In Ruby 3, keyword arguments has to be splat into its own using double splat.

See https://www.ruby-lang.org/en/news/2019/12/12/separation-of-positional-and-keyword-arguments-in-ruby-3-0/

This fixes the following error:

in `initialize': wrong number of arguments (given 2, expected 1; required keyword: foo) (ArgumentError)

[lulalala]

Sorry I am still yet to write test for this, don't merge just yet.