Add a minimalistic linter action

.github/workflows/lint.yml

@@ -0,0 +1,17 @@
+name: clang-format Check
+on: [push, pull_request]
+jobs:
+  formatting-check:
+    name: Formatting Check
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+      fail-fast: true
+    steps:
+      - uses: actions/checkout@v4
+      - name: Run clang-format style check for C/C++/Protobuf programs.
+        uses: jidicula/[email protected]
+        with:
+          clang-format-version: "19" # latest on Archlinux as of committing
+          check-path: "sources"

sources/CONTRIBUTION.md

@@ -1,4 +1,6 @@
 # Contribution Guide
 
-It is suggested for the new contributors to use the following tools:
-- `clang-format` for all the C files, source and headers.
+This project enforces (see [workflows](../.github/workflows/)) the following
+formatters:
+- `clang-format` version 19 for all the C files, source and headers (or any
+  protobuf if any, in the future).