Add window resize handler

[vorg]

We need to add the callback handler

onWindowResize: function(e) {
}

[dmnsgn]

Do we? We're already checking the ctx dimensions:

  const w = this._ctx.gl.drawingBufferWidth
  const h = this._ctx.gl.drawingBufferHeight
  let resized = false
  if (w !== this._viewport[2] || h !== this._viewport[3]) {
    this._viewport[2] = w
    this._viewport[3] = h
    resized = true
  }