document how the demo.gif was created
Unfortunately, I don't remember the exact commands but this should
suffice
- [json-kv](https://github.com/aurule/json-kv)
- [Sublime Packages](https://github.com/sublimehq/Packages/tree/fa6b8629c95041bf262d4c1dab95c456a0530122)
- [ansi-dark theme](https://github.com/sharkdp/bat/blob/master/assets/themes/ansi-dark.tmTheme)
+
+## Tools used to create xh-demo.gif
+- [asciinema](https://github.com/asciinema/asciinema) for the initial recording.
+- [asciinema-edit](https://github.com/cirocosta/asciinema-edit) to speed up the recording.
+- [asciicast2gif](https://github.com/asciinema/asciicast2gif) to produce the final GIF. The
+ default font didn't look great so I modified it to use [Cascadia Mono](https://github.com/microsoft/cascadia-code).
