plays videos in egui from file path or from bytes

as of now, can't publish as a crate due to me depending on a modified version of rust-ffmpeg; i'm waiting for response on the corresponsing PR. for now, you have to specify this as a git dependancy in Cargo.toml

• requires ffmpeg 6. follow the build instructions here

/* called once (top level initialization) */

{ // if using audio...
    let audio_sys = sdl2::init()?.audio()?;
    let audio_device = egui_video::init_audio_device(&audio_sys)?;
    
    // don't let audio_device drop out of memory! (or else you lose audio)

    add_audio_device_to_state_somewhere(audio_device);
}

/* called once (creating a player) */

let mut player = Player::new(ctx, my_media_path)?;

{ // if using audio...
    player = player.with_audio(&mut my_state.audio_device)
}

/* called every frame (showing the player) */
player.ui(ui, [player.width as f32, player.height as f32]);

are welcome :)

• need to compile in release or opt-level=3 otherwise limited playback performance
• bad (playback, seeking) performance with large resolution streams
• seeking can be slow (is there better way of dropping packets?)
• depending on the specific stream, seeking can fail and mess up playback/seekbar (something to do with dts?)
• no audio playback