Fix image on mobile

[MichaelCurrin]

Here we have a horizontal image which has height at 300 and it gets squashed on mobile.

[MichaelCurrin]

The default I used of 400 height was too large on desktop

I found height better to set than width as vertical space needs to be not huge when using tall or wide image. Perhaps I need to set width instead.

Or height as auto - update: that did nothing.

[MichaelCurrin]

Here is the page. https://github.com/MichaelCurrin/simplest-jekyll/blob/master/README.md

Using width instead