chore(deps): remove unused packages

package.json

@@ -30,11 +30,8 @@
   "dependencies": {
     "@reach/router": "^1.2.1",
     "gatsby": "^2.18.12",
-    "gatsby-image": "^2.2.36",
     "gatsby-plugin-layout": "^1.1.18",
     "gatsby-plugin-manifest": "^2.2.33",
-    "gatsby-plugin-mdx": "^1.0.62",
-    "gatsby-plugin-offline": "^3.0.29",
     "gatsby-plugin-prefetch-google-fonts": "^1.4.3",
     "gatsby-plugin-react-helmet": "^3.1.18",
     "gatsby-plugin-react-svg": "^2.1.2",
@@ -69,7 +66,6 @@
     "@types/react": "^16.9.16",
     "@types/react-dom": "^16.9.4",
     "@types/react-helmet": "^5.0.14",
-    "@types/react-treeview": "^0.4.2",
     "@types/styled-components": "^4.4.1",
     "babel-plugin-styled-components": "^1.10.6",
     "discord.js": "^11.5.1",