Improve GitHub Actions (#97)

* Delete hassfest.yaml

* Update and rename ci.yaml to tox.yaml

* Create combined.yaml

* Update hacs.json

* Update README.md

* Update combined.yaml

* Remove unused import

* Restored wrongly deleted line in cover.py

* Update config_flow.py

* Update __init__.py

Co-authored-by: Pierre Ståhl <pierre.staahl@gmail.com>
Co-authored-by: rospogrigio <49229287+rospogrigio@users.noreply.github.com>

.github/workflows/tox.yaml

@@ -0,0 +1,30 @@
+name: Tox PR CI
+
+on: [pull_request]
+
+jobs:
+  build:
+    name: >-
+      ${{ matrix.python-version }}
+      /
+      ${{ matrix.platform }}
+    runs-on: ${{ matrix.platform }}
+    strategy:
+      matrix:
+        platform:
+          - ubuntu-latest
+        python-version:
+          - 3.7
+          - 3.8
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade setuptools pip
+        python -m pip install tox-gh-actions
+    - name: Run tox
+      run: tox -q -p auto