Make it easy to pick typographic "theme" in blog starter

[KyleAMathews]

Need to publish themes as separate module to NPM for typography.js then can integrate into blog starter so can pick theme in config.toml.

KyleAMathews/typography.js#10 (comment)

[KyleAMathews]

It'd be fun actually to create a dev-only component which floats on the screen and let's you easily select between different themes.

[KyleAMathews]

Probably not a good idea.