Suggestion for hypothes.is embed ... it 'pops up' by default

[daaronr]

To nudge people slightly towards this, you can add to the index.Rmd:

      in_header: [header_include.html]

And in that header_include.html file, include

<script async defer src="https://hypothes.is/embed.js"></script>

I do this here in my Writing Economics book