Add support for associative arrays (v1.1.0+)

[ZacharyWesterman]

This would likely need to have similar syntax to PHP's associative array definitions, e.g.

let object = {
  'a' => 1,
  'b' => 2,
  'c' => 3,
}

Also need a way to define empty assoc arrays, maybe something like let object = {=>}?

Importantly, associative arrays and regular arrays should NOT be allowed to mix.

[ZacharyWesterman]

Probably just call them objects, not tables or associative arrays.