Feature: Show image annotations markers in sequencer

Description of feature

• Show image annotations markers in sequencer.
  • Pending image annotations are taller and a bit transparent.

Refactor

• build_sequence_overlays has been split into build_sequence_status and build_sequence_annotation_markers.

UI

• Image annotation marker color for both actual and pending can be customized in configuration.

Basic design

Pending annotations

Configuration

How to test it

Link review with image annotations or draw over a media.

Checklist

Please check if your MR fulfills the following requirements:

• Unit tests have been added, if possible
• Documentation has been updated
• Build was run locally and any changes were pushed
• Lint has passed locally without error
• CHANGELOG.md has been updated

FYI: @strangenoise