Add a TimeLine UI node

[JekSun97]

Describe the project you are working on

Animation editor

Describe the problem or limitation you are having in your project

I have a few projects that need this, the first one is a small game editor that really needs Timeline.
I tried to implement this myself, but why reinvent the wheel when there is already an existing Timeline animation editor.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

I propose to open a new UI node called Timeline, as it once happened with GraphEdit.
It would be quite a useful node and it has many ways of application, for example:

1. Game editor/Game engine
2. Music editor
3. Plugins
4. Particle behavior

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

I haven't looked at the source code of the Timeline animation editor yet, but I think it can be expanded in the same way as GraphEdit.

If this enhancement will not be used often, can it be worked around with a few lines of script?

No

Is there a reason why this should be core and not an add-on in the asset library?

Godot has a lot of helper nodes that could be part of a plugin, but they are there because the community finds them useful, the same goes for Timeline.

[AThousandShips]

See:

• Expose AnimationTrackEditor and AnimationTrack* related classes #3468