Make useful for perf regression testing

[japgolly]

use case: Every time library X is release, BM results are recorded and compared with history.

Will be hard to account for environmental changes.

Anyhoo, would be a nice-to-have.

[japgolly]

Idea: SJS build, save output JS as artifact, exports statically-named fn that provides BM and metadata.
Allows BMs between multiple versions of Scala & Scala.JS. No need to store results or worry about env/hardware because it's stateless.