Enable geckodriver for tests

Author: mpasternak

.github/workflows/tests.yml

@@ -14,6 +14,7 @@ jobs:
 
  steps:
  - uses: actions/checkout@v1
+ - uses: browser-actions/setup-geckodriver@latest
  - name: Set up Python ${{ matrix.python-version }}
  uses: actions/setup-python@v2
  with: