Up dependency version of JSON::Marshal

Up dependency version of JSON::Unmarshal

Release for v0.0.19

Add opt-in marshalling

Up version of JSON::Marshall

Accept :pretty adverb for JSON::Marshal -> JSON::Fast

Up minimum version of JSON::Marshal

Remove a todo test

Specify minimum versions of dependencies

Also Raku it up.

Pass on the :sorted-keys adverb supplied to to-json

This addresses jonathanstowe/META6#15

Remove :api adverb to appease ancient rakudo