Add version requirements

README.md

 # gatsby-plugin-typegen
+
 Code generate for ALL your Gatsby nodes
+
+## Requirements
+
+- Node v10.0.0 +
+- GatsbyJS v2 +

package.json

@@ -5,6 +5,9 @@
   "repository": "https://github.com/cometkim/gatsby-plugin-typegen.git",
   "author": "Hyeseong Kim <cometkim.kr@gmail.com>",
   "license": "MIT",
+  "engines": {
+    "node": ">=10.0.0"
+  },
   "scripts": {
     "build": "babel gatsby-* -d . --extensions .ts,.tsx",
     "prepublishOnly": "yarn build"