Implement metadata generation functionality

Cargo.lock

Cargo.toml

src/ffmpeg_api/api.rs

src/ingest/extract.rs

src/ingest/mod.rs

src/ingest/spritesheet.rs

src/main.rs

src/util/media_time.rs

src/util/mod.rs

src/util/stream_metadata.rs

src/util/webvtt.rs