Feature: Structured JSON-like data

This is a very distant future feature, perhaps for ink v3, which is likely to be years rather than months away!

Add the ability to put more complex data structures within ink by including nestable arrays and dictionaries, and standard dot syntax to reference them.

Would be good if the syntax was a superset of JSON, so it's possible to copy/paste data easily from other sources. YAML itself isn't quite right and would have collisions with ink syntax, but something along those lines would be good.

Note that adding something like this is a bit of a can of worms, since we may need a full set of standard library functions for manipulating the data structures (adding/removing elements, finding the index of elements, etc). It would create a whole new set of expectations that ink should be usable as a general purpose programming language.