Ability to signal EXT-X-ENDLIST in manifest

[birme]

To simulate an event it should be possible to configure the engine to insert an EXT-X-ENDLIST tag in the manifest [1]. If the engine is initiated with the option { event: true } it will insert an EXT-X-ENDLIST at the end of the manifest when no new VOD is received by the nextVod() call within an iteration.

[1] https://developer.apple.com/documentation/http_live_streaming/example_playlists_for_http_live_streaming/event_playlist_construction