Add `?autorun` parameter to run tests automatically on load

[caugner]

Use case: When determining the version in mdn/browser-compat-data#26484, I would have liked to open https://mdn-bcd-collector.gooborg.com/tests/api/EXT_shader_texture_lod?autorun in BrowserStack Live, and simply switch between browser versions to see the results, without having to click "Run" and wait for the results. This could save significant time when testing multiple browser versions.

[queengooborg]

The reason for the button to click is because some tests cannot run without a user interaction to trigger them. An auto-run would cause a number of tests to fail and return null because they don't have the permissions needed.