Run typechecker on CI

.github/workflows/main.yml

@@ -40,3 +40,17 @@ jobs:
 
       - name: Run linter
         run: flake8 ./src
+
+  typechecker:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Install dependencies
+        run: sudo apt-get update && sudo apt-get install -y python3 python3-pip
+
+      - name: Run build
+        run: pip3 install .[dev]
+
+      - name: Run typechecker
+        run: mypy

pyproject.toml

@@ -36,3 +36,13 @@ markers = [
   "overnight: for tests that take hours to complete (deselect with '-m \"not overnight\"')",
   "serial"
 ]
+
+[tool.mypy]
+files = ["src"]
+ignore_missing_imports = true
+strict_optional = true
+allow_untyped_calls = false
+warn_return_any = true
+warn_unused_ignores = true
+disallow_untyped_defs = false
+strict = true