fix: CI only publish on master

.woodpecker.yml

@@ -1,12 +1,18 @@
-pipeline:
-  backend:
+steps:
+  test:
     image: rust
     commands:
-      - apt update && apt-get -y --no-install-recommends install tar gpg curl wget git
       - rustup component add rustfmt
       - rustup component add clippy
       - make lint
       - make test
       - make doc
+  publish:
+    image: python
+    when:
+      event: [push, tag, deployment]
+      branch: master
+    commands:
+      - apt update && apt-get -y --no-install-recommends install tar gpg curl wget git
       - make ci-deploy
     secrets: [ GITEA_WRITE_DEPLOY_KEY, LIBREPAGES_DEPLOY_SECRET ]