fix(docz-core): initialize config state on data server start (#678)

In a project with no docz config files, (for example,
in a gatsby app using gatsby-theme-docz with config only
in gatsby-config.js), the config state is not initialized,
which causes errors when the config state is read.

core/docz-core/src/states/config.ts

@@ -56,7 +56,7 @@ export const state = (config: Config): State => {
     id: 'config',
     start: async params => {
       const fn = async () => update(params, initial)
-
+      await update(params, initial)
       watcher.on('add', fn)
       watcher.on('change', fn)
       watcher.on('unlink', fn)