ci: add weekly rebuild

This ensures our project keeps building and that there is always a package
produced by our CI onmaster branch available.

.github/workflows/rebuild.yml

@@ -0,0 +1,19 @@
+# SPDX-FileCopyrightText: 2024 Roman Gilg <[email protected]>
+# SPDX-License-Identifier: MIT
+name: Weekly Project Rebuild
+on:
+  schedule:
+    - cron: '0 5 * * 4'
+jobs:
+  build:
+    if: github.repository == 'winft/theseus-ship'
+    uses: ./.github/workflows/build.yml
+    with:
+      image: registry.gitlab.com/kwinft/ci-images/archlinux/kwinft-base-master
+
+  package:
+    uses: ./.github/workflows/package.yml
+    needs: build
+    with:
+      image: registry.gitlab.com/kwinft/ci-images/archlinux/kwinft-base-master
+      package-name: theseus-ship