Add new standards for theme contributions

[rdwatters]

This is already partially improved from the currently published site. See this thread for @bep's suggestion to include minimal visual descriptions for every theme. This is an important accessibility consideration:

https://discuss.gohugo.io/t/theme-recommendations/5816/4

I think the easiest way to take care of this will be to establish some tighter (but not discouraging) editorial/submission guidelines for how theme creators can build a really good README in addition to theme.toml.

Any thoughts, @digitalcraftsman?

See also in main repo:

https://github.com/spf13/hugoThemes/issues/226

[ghost]

@rdwatters I subbed a pull to update the docs (it was easier than creating an issue). Unfortunately I refuse to sign contracts to perform open source development so please consider forking my work and resubmitting the pull so it may be merged when its merged. Trims! (That's short for Terima Kasih.)

https://github.com/gohugoio/hugoThemes/pull/379

I just saw this repo was a poc. Har har.