Benchmark package initial release

[hassila (Joakim Hassila)]

And now it's shipped, please see the announcement here for details:

Package-benchmark 0.6.0 released

I'm happy to share a new version (0.6.0) of the package-benchmark SwiftPM command plugin - this release has one major feature and addresses one of the most common sources of confusion of the results - it's now based on the newly released package-histogram greatly improving the experience when you have a wide range of values that are being captured. The previous version of package-benchmark would have a range of linear buckets (and take the first sample to choose magnitude) and fall back on powe…