restore helm chart repo index after docusaurus in travis

Author: Knappek

.travis.yml

@@ -55,6 +55,7 @@ jobs:
         - git config --global user.email "${GH_EMAIL}"
         - echo "machine github.com login ${GH_NAME} password ${GH_TOKEN}" > ~/.netrc
         - cd website && yarn install && GIT_USER="${GH_NAME}" yarn run publish-gh-pages
+        - git checkout gh-pages && git checkout $(git rev-list -n1 HEAD -- index.yaml)~1 -- index.yaml && git add index.yaml && git commit -m "Auto-restore Helm chart repo index after Docusaurus publish" && git push --verbose
     - stage: sourcedocs
       <<: *elixir-env
       script: