Emote animations support

[avaer]

Exokit Avatars loads .unitypackage files, but the animations seem separate from the actual FBX models.

If we want emotes, I think we'd need to parse the .anim YAML files in the pacakges and inject them into the THREE.js animation system, which should be able to handle the mixing. The YAML files look like this:

%YAML 1.1
%TAG !u! tag:unity3d.com,2011:
--- !u!74 &7400000
AnimationClip:
  m_ObjectHideFlags: 0
  m_PrefabParentObject: {fileID: 0}
  m_PrefabInternal: {fileID: 0}
  m_Name: Dab
  serializedVersion: 6
  m_Legacy: 0
  m_Compressed: 0
  m_UseHighQualityCurve: 0
  m_RotationCurves: []
  m_CompressedRotationCurves: []
  m_EulerCurves: []
  m_PositionCurves: []
  m_ScaleCurves: []
  m_FloatCurves:
  - curve:
      serializedVersion: 2
      m_Curve:
      - serializedVersion: 2
        time: 0
        value: -0.012714
        inSlope: 0.17463881
        outSlope: 0.17463881
        tangentMode: 0
      - serializedVersion: 2
        time: 0.033333335
        value: -0.0068927067
        inSlope: 0.25062943
        outSlope: 0.25062943
        tangentMode: 0

[avaer]

With this, we could probably have both keyboard and VR controls to trigger the emotes in the list.