[Request] support subscript `[]`operator overloading

Recently operator overloading was added, operations like +, -, *, / amongst other things were added. I noticed however that [] was not a part of this change, and was wondering if it were possible to add.

Basically, it should functions basically how get/set works, for list, map, and other custom objects, accepting the key type and either returning a value or set the value.

List<String> strList = ...;

strList[0]; // List#get(int)
strList[0] = "Hello"; // List#set(int, String)

Map<String, Value> strMap = ...;

strMap["Put"] = new Value(...); // Map#put(String, Value)
strMap["Get"]; // Map#get(String)

[rsmckinney]

@Frontear Several additional operators are under consideration, these include:

• increment/decrement: ++ and --
• compound assignment: +=, *=, etc.
• subscript: [], [] = If implemented, a[x] compiles as a.get(x), and a[x] = b compiles as a.set(x, b). Note you could add extension methods to existing classes to satisfy get/set methods e.g., add set(K, V) to Map, which delegates to put(K, V).

[rsmckinney]

Release 2020.1.34 implements operator overloading for:

• prefix/postfix increment/decrement operators ++ and --
• compound assignment: operators +=, -=, *=, /=, %=,
• index operator [], both access and assignment

Please see Operator Overloading documentation for details.