message: perf(WorkerPool): Prefer most-recently-used worker
  Re-use the last-used worker. This results in a preference for a spawned
  worker and compiled wasm over replacing a `null` queue entry.
diff: @@ -16,7 +16,7 @@ class WorkerPool {
  // proposal accepted and supported by default in Babel.
  addTask (resultIndex, taskArgs) {
  if (this.workerQueue.length > 0) {
  - const worker = this.workerQueue.shift()
  + const worker = this.workerQueue.pop()
  this.runningWorkers++
  this.fcn(worker, ...taskArgs).then(({ webWorker, ...result }) => {
  this.workerQueue.push(webWorker)
  