Add image build workflow

.forgejo/workflows/build-image.yaml

@@ -0,0 +1,25 @@
+on:
+  push:
+
+
+jobs:
+  oci-builder:
+    name: 'Build oci-builder'
+    runs-on: 'oci-builder'
+
+    steps:
+      - uses: 'actions/checkout@v4'
+
+      - name: 'Build image'
+        uses: 'redhat-actions/buildah-build@v2'
+        with:
+          image: 'registry.uncontrol.me/ver4a/oci-builder'
+          containerfiles: 'Dockerfile'
+          oci: true
+          extra-args: |
+            userns=container
+            security-opt=no-new-privileges
+            annotation=quay.expires-after=
+          build-args: |
+            REGISTRY_DOMAIN=${{ vars.REGISTRY_DOMAIN }}
+            NAMESPACE=${{ vars.NAMESPACE }}