Timeline

[BBlaza]

Finished the basic setup of the timeline, completed the following features:

Display each frame in order
Allow the user to make a selection of layers in the timeline

The lower half of the timeline panel is left for the audio timeline

All the features have been implemented. This Pr should implement the following feature requests:
#4
#23

[jordanbrotherton]

Really good work here! In my testing and review most of all seems good. There are however some blockers that need to be addressed:

• I noticed you added an index to the create_layer method, and when you call it in the timeline_manager.gd file, you did not specify a color. Passing TRANSPARENT before the index should fix this.
• The timeline is completely empty when you load an existing project, only when you add a new page will the timeline appear. It seems calling setup_image_timeline() when you attach a valid project fixes this issue.
• Slightly more minor but I noticed that GUT was modified by a formatter, please revert that change to avoid conflicts.

Once these issues are addressed, it should be good to merge! Once again, really good PR!

[BBlaza]

@jordanbrotherton All done! Should be ready to be merged.

[jordanbrotherton]

Looks good, merged!