function filterArtifactsByGatherMode(artifacts, mode) {
  if (!artifacts) return null;
  return artifacts.filter(artifact => {
    return artifact.gatherer.instance.meta.supportedModes.includes(mode);
  });
}
Filters an array of artifacts down to the set that supports the specified gather mode.

@param {LH.Config.ResolvedConfig['artifacts']} artifacts
@param {LH.Gatherer.GatherMode} mode
@return {LH.Config.ResolvedConfig['artifacts']}