👷 github: workflows: Add REUSE Compliance Check

Maybe we can avoid issues like #16 with this in the future?

Link: https://github.com/marketplace/actions/reuse-compliance-check

Author: LeSpocky

.github/workflows/reuse.yml

@@ -0,0 +1,18 @@
+# SPDX-FileCopyrightText: 2022 Free Software Foundation Europe e.V. <https://fsfe.org>
+# SPDX-License-Identifier: CC0-1.0
+---
+name: REUSE Compliance Check
+
+on: [push, pull_request]
+
+permissions:
+  contents: read
+
+jobs:
+  reuse-compliance-check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: REUSE Compliance Check
+        uses: fsfe/reuse-action@v5