Chrome headless for more stable & CI-supported E2E testing

E2E testing currently uses a locally-installed browser and cannot be ran on a headless CI. Using a locally-installed browser is:

  1. annoying
  2. resource-intensive
  3. not feasible on CI

Chrome has recently started to support running the browser headlessly, which will fix these issues. However, it's not very well supported yet (still Alpha~Beta stage). This is a tracking issue for widespread support.

See: