[feature] audio playback

[syoyo]

Initial audio playback feature has been added to miniaudio branch: https://github.com/lighttransport/gltf-insight/tree/miniaudio

We use MSFT_audio_emitter extension to load audio file from a glTF model: KhronosGroup/glTF#1400

TODO

• Display audio waveform/spectrogram to sequencer
• Sync audio playback with animation sequence/animation clip
• animation event support
• spatial audio

Optional

• Switch to use Soloud https://github.com/jarikomppa/soloud audio library for easier audio manipulation

[cesss]

I don't know how do you manage to know the existence of miniaudio and Soloud. I didn't know that such two jewels existed!!