Add Zola example (#53)

An example workflow to push pages built with [Zola](https://www.getzola.org) to Codeberg Pages.

Reviewed-on: https://codeberg.org/Codeberg-CI/examples/pulls/53
Reviewed-by: 6543 <6543@obermui.de>
Co-authored-by: daudix <ddaudix@gmail.com>
Co-committed-by: daudix <ddaudix@gmail.com>

Zola/.woodpecker.yaml

@@ -0,0 +1,53 @@
+# Takes a repository with Zola source, generates the static site and
+# pushes the result to the pages branch of the same repository
+#
+# Must be set in Woodpecker configuration:
+# mail: Your email address used by Codeberg
+# codeberg_token: Codeberg access token with "write:repository" permission
+#
+# .domains file can be put inside static folder in Zola source
+#
+
+# Exclude the pipeline to run on the pages branch
+when:
+  branch:
+    exclude: pages
+
+# Clone recursively to fully clone the themes given as Git submodules
+clone:
+  git:
+    image: woodpeckerci/plugin-git
+    settings:
+      recursive: true
+
+steps:
+  # Build Zola static files
+  build:
+    image: alpine:edge
+    commands:
+      - apk add zola
+      - zola build
+    when:
+      event: [push, pull_request]
+
+  publish:
+    image: bitnami/git
+    secrets: [mail, codeberg_token]
+    commands:
+      # Configure Git
+      - git config --global user.email $MAIL
+      - git config --global user.name "Woodpecker CI"
+      # Clone the output branch
+      - git clone --branch pages https://$CODEBERG_TOKEN@codeberg.org/$CI_REPO.git $CI_REPO_NAME
+      # Enter the output branch
+      - cd $CI_REPO_NAME
+      # Remove old files
+      - git rm -r "*" || true # Don't fail if there's nothing to remove
+      # Copy the output of the build step
+      - cp -ar ../public/. .
+      # Commit and push all static files with the source commit hash
+      - git add --all
+      - git commit -m "Woodpecker CI ${CI_COMMIT_SHA} [SKIP CI]" --allow-empty
+      - git push
+    when:
+      event: [push]