Implement new function

[Vercix]

This pull request would implement the new function. This will create a more convenient API for instantiating JavaScript classes in GDScript.

For example:

var ControllerApp = preload("res://dist/GodotFreApp.jsx")

# Called when the node enters the scene tree for the first time.
func _ready():
	var x = ControllerApp.new(1, null, 'some_other_prop', self)
	add_child(x)

This is related to #107

There is a few things that I am not happy about with this implementation, though.

• I created a new method for the QuickJS binder class, create_ecma_instance_for_godot_object_args, which is essentially a copy of create_ecma_instance_for_godot except that it accepts args. Which are converted into JSValues and then passed to JS_CallConstructor2. I removed the initialize_properties call in the new function which is used in the original function to set properties registered through godot.register_property. Because they are set to null when instantiating through new(). There probably is a better way of handling this though.
• There probably should be some error checking to see if the Godot class the JavaScript class inherits from exists in emcascript.cpp.

Looking forward to review and suggestions.