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

To nudge people slightly towards this, you can add to the index.Rmd: 

```    includes:
      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](https://daaronr.github.io/writing_econ_research/introduction.html)

