feat: cascade for table/json obj

[hugosenari]

Would be cool if it has any syntax sugar for []=

import cascade
import json

let myObj = cascade newJObject:
    myAttr = "myValue"
    myOther = cascade newJObject:
        innerAttr = "innerValue"
    myArray = cascade newJArray:
        - "first value"
        - "second value"

Maybe I just need a YAML but it has so nice features if/when and nice DSL for write JSON/YAML

[haltcase]

Seems cool, I'd accept a PR for this (I won't have the time to implement it myself currently).

I'm not sure about the unary - however, that would be a separate issue for RFC.

Edit: this would have to be disambiguated from the current assignment syntax, which is unconditionally transformed to a dot expression.