Remove /404 & /[...slug] from sitemap

scripts/generate-sitemap.js

@@ -28,6 +28,9 @@ const siteMetadata = require('../data/siteMetadata')
                   .replace('.md', '')
                   .replace('/index.xml', '')
                 const route = path === '/index' ? '' : path
+                if (page === `pages/404.js` || page === `pages/[...slug].js`) {
+                  return
+                }
                 return `
                         <url>
                             <loc>${`${siteMetadata.siteUrl}${route}`}</loc>