build: add github action to run ruff

.github/workflows/pr.yaml

@@ -0,0 +1,30 @@
+name: PR validation
+
+on: [pull_request]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Install poetry
+        run: pipx install poetry
+
+      - name: Set up Python
+        uses: actions/[email protected]
+        with:
+          python-version: "3.12"
+          cache: "poetry"
+          cache-dependency-path: "poetry.lock"
+
+      - name: Install dependencies
+        run: poetry install
+
+      - name: Run code linters
+        run: |
+          poetry run ruff check discobuilder
+          poetry run ruff format --check discobuilder