Prepare release 1.6.0

[jgonggrijp]

I realized there was some unfinished work lying around, which deserved a release.

After an approving review, I will add another commit with the generated files (i.e., docco and the minified code) and then upload the release to NPM.

@stephenkao I saw your response to #4268 and wanted to send you a formal review request, but GitHub's Reviewers form field would not let me do it. I hope a mention works for you.

[jgonggrijp]

@Rayraz could you take a look?

[jgonggrijp]

Thanks @paulfalgout! 🙏

[stephenkao]

Ah, sorry, @jgonggrijp! I've been a little busy the last couple of weeks, but I'm open to check out future pull requests in the future. Glad there was a happy ending here :)