Use Gatsby SiteMetadata for plausible domain and src

Author: rogermparent

packages/gatsby-theme-iterative/gatsby-config.js

@@ -171,10 +171,6 @@ module.exports = ({
     }
   ],
   siteMetadata: {
-    author: '',
-    siteUrl: '',
-    titleTemplate: '',
-    plausibleSrc: 'https://plausible.io/js/plausible.outbound-links.js',
-    plausibleDomain: ''
+    plausibleSrc: 'https://plausible.io/js/plausible.outbound-links.js'
   }
 })

packages/gatsby-theme-iterative/gatsby-node.js

@@ -57,6 +57,16 @@ exports.createSchemaCustomization = async api => {
         name: 'String!',
         match: '[String]'
       }
+    }),
+    buildObjectType({
+      name: 'SiteSiteMetadata',
+      fields: {
+        author: 'String',
+        siteUrl: 'String',
+        titleTemplate: 'String',
+        plausibleSrc: 'String',
+        plausibleDomain: 'String'
+      }
     })
   ])
 }