Add no-floating-promises rule, disabled for now

https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-floating-promises.md

Author: sindresorhus

index.js

@@ -165,6 +165,10 @@ module.exports = {
 		// ],
 
 		'@typescript-eslint/no-extraneous-class': 'error',
+
+		// Disabled because of https://github.com/typescript-eslint/typescript-eslint/issues/647
+		// '@typescript-eslint/no-floating-promises': 'error',
+
 		'@typescript-eslint/no-for-in-array': 'error',
 		'@typescript-eslint/no-inferrable-types': 'error',
 		'@typescript-eslint/no-misused-new': 'error',