chore(deps): update gatsby monorepo

Author: renovate-bot

package.json

@@ -12,15 +12,15 @@
     "@mdx-js/mdx": "1.6.18",
     "@mdx-js/react": "1.6.18",
     "classnames": "2.2.6",
-    "gatsby": "2.24.68",
-    "gatsby-image": "2.4.21",
-    "gatsby-plugin-mdx": "1.2.44",
-    "gatsby-plugin-postcss": "2.3.13",
-    "gatsby-plugin-react-helmet": "3.3.13",
+    "gatsby": "3.8.0",
+    "gatsby-image": "3.8.0",
+    "gatsby-plugin-mdx": "2.8.0",
+    "gatsby-plugin-postcss": "4.7.1",
+    "gatsby-plugin-react-helmet": "4.7.1",
     "gatsby-plugin-react-svg": "3.0.0",
-    "gatsby-plugin-sharp": "2.6.39",
+    "gatsby-plugin-sharp": "3.8.0",
     "gatsby-source-graphcms": "2.0.0-next.11",
-    "gatsby-transformer-sharp": "2.5.17",
+    "gatsby-transformer-sharp": "3.8.0",
     "react": "16.13.1",
     "react-dom": "16.13.1",
     "react-helmet": "6.1.0",