Enable Table of Contents / Chapters

[OpenHypervideo]

Add functionality for chapters / table of contents (time ranges within a hypervideo)

• Decide on data format (custom, WebVTT, IIIF A/V TOC, ...)
• Visual editor for chapters
• ContentView type Table of Contents, which renders TOC depending on the context (small, medium and large ContentViews, being positioned at the top/bottom or left/right)

[OpenHypervideo]

Chapters have been implemented, incl. chapter editor. What's missing for this is the ContentView type Table of Contents, which renders the chapters depending on the context (small, medium and large ContentViews, being positioned at the top/bottom or left/right).