ci: periodically run update-generated

This introduces a GitHub workflow to periodically run `cargo xtask
update-generated` in order to keep the docs up-to-date with the
latest changes. It will create a PR if changes are detected.

Signed-off-by: Micah Abbott <[email protected]>

Author: miabbott

.github/workflows/udpate-generated.yml

@@ -0,0 +1,52 @@
+name: 'Update Generated Files'
+
+# This workflow is triggered on a schedule (every day at 3:15 AM UTC)
+# and can also be triggered manually from the GitHub Actions UI.
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: '15 3 * * *'
+
+jobs:
+  update-and-pr:
+    name: 'Update Generated Files and Create PR'
+    runs-on: ubuntu-latest
+    container: quay.io/coreos-assembler/fcos-buildroot:testing-devel
+    steps:
+      - name: 'Checkout repository'
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: 'Mark git directory as safe'
+        run: git config --global --add safe.directory "$GITHUB_WORKSPACE"
+        shell: bash
+
+      - name: 'Install dependencies'
+        run: ./ci/installdeps.sh
+        shell: bash
+
+      - name: 'Install pandoc'
+        run: dnf -y install pandoc
+        shell: bash
+
+      - name: 'Update generated docs'
+        run: cargo xtask update-generated
+        shell: bash
+
+      - name: 'Create Pull Request'
+        uses: peter-evans/create-pull-request@v6
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          commit-message: 'chore: Update generated files'
+          committer: 'github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>'
+          author: 'github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>'
+          signoff: true
+          title: 'docs: Update generated'
+          body: |
+            This PR was auto-generated by a GitHub Actions workflow.
+
+            It contains updates to doc files generated by `cargo xtask update-generated`.
+          branch: 'actions/update-generated-files'
+          labels: 'documentation'
+