Build breaks if content does not include readme or index

[boygirl]

If there is not an index or readme inluded in the content directory, and no links anywhere on the site to the base route (i.e. /docs/), this plugin will work in dev mode, but will fail to build for production / staging.

[kitten]

Yea, I've noticed that 😓 It's a limitation in react-static that I'll have to add a workaround for

[boygirl]

I think it's a pretty understandable limitation. I just opened this for the benefit of future folks.