Add tests for dashboard

[vsoch]

Aside from it returning (e.g., starting the dashboard and pinging endpoints to see 200 status) I'd like to add tests that can start the dashboard (before or after running tasks), and then take screenshots of the virtual browser to check various views. This will be more important as more executors are developed (possibly with executor-specific views). GitHub actions with workflow artifacts might work, but something like CircleCI to generate a report that we can click on to see would be better.