fix(gatsby-theme-docz): use options from gatsby-config (#665)

The gatsby-node `onPreInit` hook passes in two arguments, the _second_ of which is the plugin options.

core/gatsby-theme-docz/src/node/onPreInit.js

@@ -17,7 +17,7 @@ const touchTemplateWithPaths = paths => async (filepath, opts) => {
   await touch(dest, raw)
 }
 
-module.exports = async opts => {
+module.exports = async (_, opts) => {
   const { paths, ...config } = await parseConfig(opts)
   const componentPath = mountComponentPath(paths)
   const touchTemplate = touchTemplateWithPaths(paths)