Enable GHA CI check for Mypy type annotations

Author: reivilibre

.github/workflows/ci.yml

@@ -16,16 +16,16 @@ jobs:
       #- run: python -m pip install tox
       #- run: tox -e check_codestyle
 
-  #check-types:
-    #name: Check types with Mypy
-    #runs-on: ubuntu-latest
-    #steps:
-      #- uses: actions/checkout@v2
-      #- uses: actions/setup-python@v2
-        #with:
-          #python-version: "3.x"
-      #- run: python -m pip install tox
-      #- run: tox -e check_types
+  check-types:
+    name: Check types with Mypy
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+        with:
+          python-version: "3.x"
+      - run: python -m pip install tox
+      - run: tox -e check_types
 
   unit-tests:
     name: Unit tests