fix(package): update gatsby-plugin-sharp to version 2.0.12

Closes #26

Author: greenkeeper[bot]

package.json

@@ -20,7 +20,7 @@
     "gatsby-plugin-offline": "^1.0.12",
     "gatsby-plugin-react-helmet": "^2.0.4",
     "gatsby-plugin-react-next": "^1.0.8",
-    "gatsby-plugin-sharp": "^1.6.25",
+    "gatsby-plugin-sharp": "^2.0.12",
     "gatsby-plugin-sitemap": "^1.2.13",
     "gatsby-plugin-styled-components": "^2.0.5",
     "gatsby-plugin-typography": "^1.7.13",