Add CI job to automatically run pre-commit on the diff to ensure all

changes are up to standard

Author: vulder

.github/workflows/pre-commit.yml

@@ -0,0 +1,18 @@
+name: pre-commit
+
+on:
+  pull_request:
+
+jobs:
+  pre-commit:
+    runs-on: ubuntu-20.04
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+
+    - uses: actions/setup-python@v2
+
+    - uses: pre-commit/action@v2.0.0
+      with:
+        extra_args: --from-ref origin/vara-dev --to-ref HEAD