chore: add GitHub workflow to run Mypy

.github/workflows/lint.yml

@@ -0,0 +1,44 @@
+---
+name: Linting
+
+on:
+  push:
+    paths-ignore:
+      - 'aider/website/**'
+      - README.md
+      - HISTORY.md
+    branches:
+      - main
+  pull_request:
+    paths-ignore:
+      - 'aider/website/**'
+      - README.md
+    branches:
+      - main
+
+jobs:
+  mypy:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Check out repository
+      uses: actions/checkout@v4
+
+    - name: Set up Python 3.12
+      uses: actions/setup-python@v5
+      with:
+        python-version: "3.12"
+
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install mypy
+        pip install '.[dev]'
+
+    - name: Run Mypy
+      uses: wearerequired/lint-action@v2.3.0
+      with:
+        github_token: ${{ secrets.GITHUB_TOKEN }}
+        mypy: true
+        mypy_args: "."
+        continue_on_error: false