Add mypy check, add missing types and fix type issues

.github/workflows/python_check.yml

@@ -24,12 +24,17 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        python -m pip install flake8 pylint black
+        python -m pip install -r requirements.txt
+        python -m pip install -r requirements_dev.txt
     - name: Lint with flake8
       run: |
         # stop the build if there are Python syntax errors or undefined names
         flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
         flake8 . --count --exit-zero --max-complexity=10 --max-line-length=88 --statistics
+    - name: Type check with mypy
+      run: |
+        touch "$(python -c 'import inspect, homeassistant, os; print(os.path.dirname(inspect.getfile(homeassistant)))')"/py.typed
+        mypy -p custom_components.hon
     # - name: Analysing the code with pylint
     #   run: |
     #     pylint --max-line-length 88 $(git ls-files '*.py')