v4.0.0

Breaking changes

• ImGuiLayer is now configured with an ImGuiConfig resource. This makes it simpler to update imgui-godot if you're using a custom configuration.
• Some method signature changes in ImGuiGD, obsolete methods removed. This probably won't affect any users.

New features

• Support Godot 4.1-beta2
• Support Godot's multi-threaded rendering model. I do not recommend using this just yet, because there are serious known bugs (particularly godotengine/godot#64766)