chore: prioritize gatsbyRoot and default to src

To avoid breaking behavior of changing src behavior we leave it working like before for people that haven't set gatsbyRoot

Author: rakannimer

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

@@ -12,7 +12,7 @@ const toOmit = ['_', '$0', 'version', 'help']
 export const doczRcBaseConfig = {
   themeConfig: {},
   src: './',
-  gatsbyRoot: './',
+  gatsbyRoot: null,
   themesDir: 'src',
   mdxExtensions: ['.md', '.mdx'],
   docgenConfig: {},

core/gatsby-theme-docz/gatsby-config.js

@@ -55,7 +55,10 @@ module.exports = opts => {
               ? `${config.paths.root}/node_modules/**/*`
               : `${config.paths.root}/node_modules/.cache/**/*`,
           ],
-          path: path.resolve(config.paths.root, config.gatsbyRoot),
+          path: path.resolve(
+            config.paths.root,
+            config.gatsbyRoot !== null ? config.gatsbyRoot : config.src
+          ),
         },
       },
       {