package.json: Add prepublishOnly script to catch last-minute issues

Author: daurnimator

package.json

@@ -12,6 +12,7 @@
 	},
 	"scripts": {
 		"lint": "eslint src/ test/",
+		"prepublishOnly": "git diff-index --quiet --cached HEAD -- && npm run lint && npm run test",
 		"test": "jest"
 	},
 	"repository": {