woodpecker: add ci

.woodpecker/.build.yaml

@@ -0,0 +1,40 @@
+---
+steps:
+  - name: build (prod)
+    image: woodpeckerci/plugin-docker-buildx
+    settings:
+      registry: git.ar21.de
+      username:
+        from_secret: REGISTRY_USER
+      password:
+        from_secret: REGISTRY_PASS
+      repo: git.ar21.de/tom/push-message-randomizer
+      platforms:
+        - linux/amd64
+        - linux/arm64
+      tags:
+        - latest
+        - ${CI_PIPELINE_NUMBER}
+    when:
+      - branch: main
+        event: push
+
+  - name: build (experimental)
+    image: woodpeckerci/plugin-docker-buildx
+    settings:
+      registry: git.ar21.de
+      username:
+        from_secret: REGISTRY_USER
+      password:
+        from_secret: REGISTRY_PASS
+      repo: git.ar21.de/tom/push-message-randomizer
+      platforms:
+        - linux/amd64
+        - linux/arm64
+      tags:
+        - experimental
+        - experimental-${CI_PIPELINE_NUMBER}
+    when:
+      - branch:
+          exclude: main
+        event: push