Godot: Add a warning when using non-typed variable

[qarmin]

Godot version:
3.1 0e27af2

Issue description:
It would be very helpful for me if will be option to show warning when using non-typed variable(constant, returning value etc.), because it is better to use only one of programming style.

Of course this should be disabled by default because not everyone use typed GDScript.

[groud]

There's already an indicator of whether or not a line is safe or not. The line number goes from gray to green if a line is safe:

But I think it needs at least a tooltip to be easier to understand.

See https://godotengine.org/article/optional-typing-gdscript

[vnen]

There's already an indicator of whether or not a line is safe or not.

Besides that, you can turn on warnings for unsafe lines in the Project Settings.

[aaronfranke]

Besides that, you can turn on warnings for unsafe lines in the Project Settings.

This can probably be closed then, if there are already warnings you can enable in settings.

[akien-mga]

Yes it seems to cover the use case.