ci: add REUSE check workflow

Src: 'https://reuse.software/dev/#github-actions'

.github/workflows/reuse.yaml

@@ -0,0 +1,12 @@
+# SPDX-FileCopyrightText: 2020 Free Software Foundation Europe e.V.
+# SPDX-License-Identifier: CC0-1.0
+name: REUSE compliance check
+on: [push, pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+      - name: REUSE Compliance Check
+        uses: fsfe/reuse-action@v6