Allow reversed words to skip changelog [skip ci] (#2021)

[Travis][] allows both "<KEYWORD> skip" and "skip <KEYWORD>", as does
[Circleci][]. I never remember which order the words should go in, so it
is a nice convenience if either order works.

[Travis]: https://docs.travis-ci.com/user/customizing-the-build/#skipping-a-build
[Circleci]: https://circleci.com/docs/2.0/skip-build/#skipping-a-build

.github/workflows/check_changelog.yml

@@ -10,4 +10,4 @@ jobs:
     - uses: actions/checkout@v1
     - name: Check that CHANGELOG is touched or PR is [ci skip]-d
       run: |
-        cat $GITHUB_EVENT_PATH | jq .pull_request.title | grep -i '\[\(\(changelog skip\)\|\(ci skip\)\)\]' ||  git diff remotes/origin/${{ github.base_ref }} --name-only | grep History.md
+        cat $GITHUB_EVENT_PATH | jq .pull_request.title | grep -i '\[\(\(changelog skip\)\|\(skip changelog\)\|\(ci skip\)\|\(skip ci\)\)\]' ||  git diff remotes/origin/${{ github.base_ref }} --name-only | grep History.md