Fix browser tests on CI

See #87 (closed) and #164 (closed)

(previously was "Re-enable chrome tests for karma")

We had previously disabled running the unit/component tests (karma/mocha/chai/enzyme tests) on the chrome browser due to issues running it headlessly on certain environments. Right now, the tests are only ran on Firefox on both the CI & locally. This MR will re-enable chrome browser testing support.

The easy part is enabling it in beat.editor's test config. It also already works locally. The hard part is enabling it on the CI.

UPDATE:

This CI will just fix browser tests not running on the CI. Chrome CI support probably won't be happening right now, bar someone else figuring it out.