Convert to TypeScript!

2.0.2

• Updated to TypeScript
• Breaking change: the Mesh option indicesPerMaterial has been removed in favor of always providing the indices per material.
  • Instead of mesh.indices holding an array of arrays of numbers, mesh.indicesPerMaterial will now hold the indices where the top
    level array index is the index of the material and the inner arrays are the indices for that material.
• Breaking change: the Layout class has changed from directly applying attributes to the Layout instance to creating an attributeMap