Release: 1.4.0 - Githubissues

[x] Branch: Starting from develop, cut a release branch named release/X.Y.Z for your changes.
[x] Changelog: Add/update the changelog in CHANGELOG.md.
[x] Props: update CREDITS.md file with any new contributors, confirm maintainers are accurate.
[x] Readme updates: Make any other readme changes as necessary in README.md.
[x] Merge: Make a non-fast-forward merge from your release branch to develop (or merge the pull request), then merge develop into stable (git checkout stable && git merge --no-ff develop).
[x] Push: Push your stable branch to GitHub (e.g. git push origin stable).
[x] Release: Create a new release, naming the tag and the release with the new version number, and targeting the stable branch. Paste the changelog from CHANGELOG.md into the body of the release and include a link to the closed issues on the milestone. The release should now appear under releases.
[x] Close milestone: Edit the milestone with release date (in the Due date (optional) field) and link to GitHub release (in the Description field), then close the milestone.
[x] Punt incomplete items: If any open issues or PRs which were milestoned for X.Y.Z do not make it into the release, update their milestone to X.Y.Z+1, X.Y+- [ ]0, X+- [ ]0.0 or Future Release.
[x] Celebrate shipping!

10up / wpcs-action