ci: add pre-commit

Signed-off-by: Filipe Laíns <lains@archlinux.org>

.github/workflows/checks.yml

@@ -0,0 +1,16 @@
+name: checks
+
+on: [push, pull_request]
+
+jobs:
+  pre-commit:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+
+    - name: Setup Python
+      uses: actions/setup-python@v2
+
+    - name: Run pre-commit
+      uses: pre-commit/action@v2.0.0