Proposal: Add class type

The Problem

There's currently no built-in way to distinguish a brighterscript class from other classes or plain assocarrays. We can manually add our own "type" property, but have to do that for every class we ever create.. and on teams with multiple members, that's also left to memory and easy to forget

Proposal

This is a similar problem that JavaScript prototypes have (which are very similar to brighterscript classes). A potential pattern that we could mirror was added in ES6:

JS ES6 solved this by adding the constructor.name property

For Brighterscript, the simplest way to add this might look like:
(transpiled)

function __exampleClass_builder()
  instance = {}
  instance._isClass = true
  instance._name = "exampleClass"
  return instance
end function

function exampleClass(args)
  instance = __exampleClass_builder()
  instance.new(args)
  return instance
end function

Value-Add

This opens up room for developers to use simple utils like [the following] to differentiate classes from eachother and other objects

function isClass (value)
  return isAssocArray(value) and (true = value._isClass)
end function

function isClassOf (value, classType)
  return isClass(value) and (value._name <> invalid) and (value._name = classType)
end function

Closing Remarks

Open to discussion/suggestions on what this should look like for Brighterscript. Once there's consensus, I don't mind doing the PR

The proposal names no implementation files, tests, or compiler entry points. First establish consensus on the class representation and type-detection behavior, then locate the BrighterScript class transpilation path and define tests that distinguish class instances from plain associative arrays.