The arXiv bookmarklet is missing in blogpost

The code for arXiv bookmarklet in [blog post](https://web.hypothes.is/show-annotations-on-arxiv/
) by @judell is missing.

It would be a nice improvement for working with arXiv papers (since the PDFs there only have code as a title).

### Steps to reproduce
1. Go to https://web.hypothes.is/show-annotations-on-arxiv/

### Expected behaviour
The bookmarklet for arXiv works (is draggable as a bookmark).

### Actual behaviour
The bookmarklet is not draggable/clickable in bot Firefox and Chromium. The source is just `

arxiv / hypothesis

`, the span is passive (e.g. no target or event listeners), .

### Browser/system information
* Ubuntu 18.04, Firefox 64.0 (64 bit) (no active extensions)
* Ubuntu 18.04, Chromium 71.0.3578.80 (no active extensions)