Add Dockerfile and workflow

.forgejo/workflows/build.yaml

@@ -0,0 +1,13 @@
+on:
+  push:
+  schedule:
+    - cron: '0 0 * */1 *'
+jobs:
+  build:
+    runs-on: gitea-container-builder
+    steps:
+      - run: apk add buildah wget
+      - run: buildah login --username ${{ secrets.username }} --password ${{ secrets.password }} ${GITHUB_SERVER_URL}
+      - run: wget ${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/raw/branch/${GITHUB_REF_NAME}/Dockerfile
+      - run: buildah build --isolation=chroot | tee container_id
+      - run: buildah push $(tail -n 1 container_id) ${GITHUB_SERVER_URL/https:\/\//}/${GITHUB_REPOSITORY,,}:latest

Dockerfile

@@ -0,0 +1,3 @@
+# hadolint ignore=DL3006
+FROM alpine:latest
+RUN apk add buildah wget