Binding to AVChapter and chapters functions in Container class

[DE-AI]

This PR adds c bindings to AVChapter struct and a method to list all chapters in a container.

Example usage:

import av
container = av.open("video_with_chapter_marks.mp4")
chapters = container.chapters()

for chapter in chapters:
    print(f"id: {chapter['id']}, start: {chapter['start']}, end: {chapter['end']}, time_base: {chapter['time_base']}, metadata: {chapter['metadata']}")

The output should look like:

id: 0, start: 0, end: 5001, time_base: 1/1000, metadata: {'title': 'I0001'}
id: 1, start: 5001, end: 10001, time_base: 1/1000, metadata: {'title': 'I0002'}
id: 2, start: 10001, end: 30000, time_base: 1/1000, metadata: {'title': 'I0003'}