Add MyPy to CI

.github/workflows/main.yml

@@ -6,9 +6,9 @@ name: Checks
 # events but only for the master branch
 on:
   push:
-    branches: [ master ]
+    branches: [master]
   pull_request:
-    branches: [ master ]
+    branches: [master]
 
 # A workflow run is made up of one or more jobs that can run sequentially or in parallel
 jobs:
@@ -47,3 +47,16 @@ jobs:
       # Prettier
       - name: Prettier
         run: node_modules/.bin/prettier -c 'src/**/*.{js,ts,tsx,css,scss}'
+
+  python:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v4
+        with:
+          python-version: "3.10"
+          cache: poetry
+      - run: poetry install --with=dev
+      - name: MyPy checks
+        run: poetry run mypy *.py