Re-add the linter

This reverts commit 82f6144.

Author: wconstab

.github/workflows/lint.yaml

@@ -0,0 +1,39 @@
+name: Lint
+
+on:
+  pull_request:
+
+concurrency:
+  group: lint-${{ github.workflow }}-${{ github.ref == 'refs/heads/main' && github.run_number || github.ref }}
+  cancel-in-progress: true
+
+defaults:
+  run:
+    shell: bash -l -eo pipefail {0}
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ['3.11']
+    steps:
+      - name: Check out repo
+        uses: actions/checkout@v3
+      - name: Setup python
+        uses: actions/setup-python@v4
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Update pip
+        run: python -m pip install --upgrade pip
+      - name: Install lint utilities
+        run: |
+          python -m pip install pre-commit
+          pre-commit install-hooks
+      - id: file_changes
+        uses: trilom/[email protected]
+        with:
+          prNumber: ${{ github.event.number }}
+          output: ' '
+      - name: Lint modified files
+        run: pre-commit run --files ${{ steps.file_changes.outputs.files }}