run reference-lib tests for PRs

[ryepup]

Is your feature request related to a problem? Please describe

Dependabot is wanting to make a bunch of small updates. The pipelines are passing, but they aren't running npm test, so we have a little lower confidence that the dependency bump is correct.

Describe the solution you'd like

Run npm test as part of the reference-lib workflow.

Describe alternatives you've considered

Manually cloning branches and running npm test by hand, but that's what robots are for.