Generate documentation snapshot for releases

Signed-off-by: Stephen Gallagher <sgallagh@redhat.com>

.github/workflows/release.yaml

@@ -0,0 +1,43 @@
+name: Release Tasks
+on:
+  release:
+    types: [published]
+
+jobs:
+  docs:
+    name: Publish Documentation
+    runs-on: ubuntu-20.04
+    continue-on-error: false
+    if: github.repository == 'fedora-modularity/libmodulemd'
+    steps:
+      - name: Checkout code repo
+        uses: actions/checkout@v2
+
+      - name: Checkout documentation repo
+        uses: actions/checkout@v2
+        with:
+          repository: fedora-modularity/fedora-modularity.github.io
+          ref: main
+          path: fedora-modularity.github.io
+          token: ${{ secrets.DOC_TOKEN }}
+
+      - name: Get release version
+        run: |
+          echo "version=$(./get_version.sh)" >> $GITHUB_ENV
+
+      - name: Generate documentation
+        run: |
+          ./.ci/ci-docs.sh $version
+
+      - name: Commit documentation
+        uses: EndBug/add-and-commit@v6
+        with:
+          branch: main
+          token: ${{ secrets.DOC_TOKEN }}
+          cwd: fedora-modularity.github.io
+          author_name: Libmodulemd CI
+          author_email: github-actions@github.com
+          message: libmodulemd docs for ${{ env.version }}
+          add: libmodulemd/${{ env.version }}
+          signoff: true
+          push: true