Disable no-undef rule

It's not compatible with optional chaining.

Author: sindresorhus

index.js

@@ -307,6 +307,9 @@ module.exports = {
 		'valid-jsdoc': 'off',
 
 		// Disabled because of https://github.com/typescript-eslint/typescript-eslint/issues/60
-		'no-redeclare': 'off'
+		'no-redeclare': 'off',
+
+		// Disabled because of https://github.com/typescript-eslint/typescript-eslint/issues/1116
+		'no-undef': 'off'
 	}
 };