ci: build docker image monthly and on push to main

.forgejo/workflows/build-docker.yaml

@@ -0,0 +1,28 @@
+on:
+  push:
+    branches:
+      - main
+  schedule:
+    - cron: '@monthly'
+
+enable-email-notification: true
+
+jobs:
+  publish-docker:
+    runs-on: ubuntu-act
+    steps:
+      - uses: https://code.forgejo.org/actions/checkout@v4
+      - name: Set up Docker Buildx
+        uses: https://code.forgejo.org/docker/setup-buildx-action@v3
+      - name: Login to Container Registry
+        uses: https://code.forgejo.org/docker/login-action@v3
+        with:
+          registry: git.ratte.dev
+          username: Laborratte5
+          password: ${{ secrets.PACKAGE_REGISTRY_TOKEN }}
+      - name: Build and push
+        uses: https://code.forgejo.org/docker/build-push-action@v6
+        with:
+          push: true
+          tags: |
+            git.ratte.dev/laborratte5/stationeers-dedicated-server:latest