Ignore built-ins and private symbols about gdscript-docs-maker

[Razoric480]

For built-in types, there's only so many: _enter_tree, _exit_tree, _input, _physics_process, _process, _ready, _unhandled_input, and _unhandled_key_input. I imagine we can maintain a dictionary for those.

Though virtual VS private is the other niggle. I'd really prefer not having double underscores. I'm already not a fan of how one looks, heh. That said, an API reference will point out functions that are public facing. Simply not adding a docstring to a function should make it essentially-private as far as a documentation generator is concerned.

Then we differentiate a virtual and private function (or a virtual private function) by the mere fact that it is or isn't documented.

[NathanLovato]

For builtins yes, I already have the list actually.

Simply not adding a docstring to a function should make it essentially-private as far as a documentation generator is concerned.

It's too easy to forget a docstring, or to document a function that shouldn't be. We shouldn't rely on us not making mistakes for the tool to work as expected.

It's a pity we don't have a virtual keyword, but at least a virtual function is one that should just pass, it shouldn't define any behavior, so I guess we can rely on that, and count the leading underscore as private otherwise.

[Razoric480]

Though with typed GDScript and virutla functions that return a value, we can't just pass - if the virtual function returns something, Godot will error out.

func _do_check() -> int: #illegal
  pass

So it's not something that can be relied upon, unless we make the base virtual function not have a return type until it's overriden in an extended class. We could explicitly tag a function as virtual in the docstring?