Split out TypeScript only lint:types npm script

Author: colinrotherham

package.json

@@ -54,10 +54,11 @@
     "build": "yarn cleanup && rollup -c",
     "test": "jest",
     "test:watch": "jest --watch",
-    "lint": "yarn lint:js",
+    "lint": "yarn lint:types && yarn lint:js",
     "lint:fix": "yarn lint:js:fix",
     "lint:js": "eslint 'src/**/*.{js,ts,tsx}' 'stories/**/*.{js,ts,tsx}'",
     "lint:js:fix": "yarn lint:js --fix",
+    "lint:types": "tsc --build tsconfig.json --pretty",
     "build-storybook": "storybook build",
     "prepublishOnly": "yarn lint && yarn test && yarn storybook --smoke-test"
   },