call function with new keyword when calling classes

[leso-kn]

This PR adds support for calling constructors!

It triggers when calling a javascript class from lua. Classes are distinguished from generic functions by the .constructor-field.

Syntax:

local ws = window.WebSocket("https://example.org")

-- ws is a new instance of WebSocket
ws.send 'hello example.org!'

[leso-kn]

@ceifa @RodrigoDornelles Linter warnings should be fixed :)

(verified here: leso-kn:wasmoon run#15605367128)