This wordpress theme is designed to be a source API for my GatsbyJs YAML starter (see wordpress branch). I use Timber for custom routes and YAML files boilerplates (see /twig/api folder). So we have special API urls https://cms.pawelwos.com/api/pages and https://cms.pawelwos.com/api/sections which are the source endpoints for gatsbyjs. Gatsby downloads these YAML files on onPreBootstrap building stage and then use them for GraphQL. This theme is taking care of changing inline links and inline images to Gatsby's <Link> and <GatsbyImage> components. It also have a preview mode which loads any CMS changes using AJAX function in wordpress so no need for any additional builds and you can check what you are creating immediately.
Demo site: https://gatsby.pawelwos.com
Demo CMS: https://cms.pawelwos.com/wp-admin
Username: tester
Password: testthis